Here is a comparison of photos for all the different Apple Watch models such as Sport and Stainless, size (32mm or 42mm) and also the colors (Aluminum vs black vs space black vs silver). There are pictures of different size wrists both large and small to help you decide which Apple Watch size to get for your wrist. I compiled a bunch of band/case combinations that several folks in /r/applewatch have tried. I was asked to put that list up here as well.

I don't expect I'll be editing this one to keep up with any updates I may see, but I will keep the linked compilation over on reddit updated as I can. Without further ado:

per request of /u/pwtercitygymleader (ps: your name is painful to type)

Now sorted by model

 Watch Sport (Aluminum)

38mm Silver Sport with White Band:



Side:(/u/tcox)

38mm sport (aluminum) with 42mm band, stainless with black sport, space grey sport with blue leather loop



(/u/iamkevski - 165mm wrist)

38mm sport with white band



(/u/maxeljulio - 155mm wrist)

38mm sport with white band



(/u/PrinceAbubu_ - 150mm wrist)

38mm sport with white band, 170mm wrist



38mm sport with white band



(/u/jaybird8491 - 185-190mm wrist)

38mm sport with white band



(/u/Techno_Hamster - 137mm wrist)

38mm sport with white band



(/u/applewatchtryon - 170mm wrist)

38mm sport with white band



(/u/slicecom)

38mm sport with white band



(/u/TVPaulD)

38mm aluminum sport with 42mm black sport band (no 38mm sport band to pair with it) http://imgur.com/a/5wu3Y

(/u/chasem13 - 170mm wrist)

38mm aluminum sport with stainless steel link band



(/u/chasem13 - 170mm wrist)

42mm (?) SS and Sport models compared, both with milanese loop



(/u/iAmManny74)

42mm Space Grey vs 38mm Silver Sport



 Watch Sport (Space Grey)

(/u/tcox)

42mm Space Grey Sport w/ Black Band Top:



(/u/tcox)

42mm Space Grey vs 38mm Silver Sport



(/u/tcox)

42mm Space Grey Sport with milanese loop



(/u/hvlchk)

42mm Space Grey Sport with black leather loop



(/u/hvlchk)

Space grey sport with milanese loop



42mm space grey sport with milanese loop



(/u/chasem13 - 170mm wrist)

42mm Sport Space Grey with blue leather loop



(/u/jdflan)

Space Grey Sport with milanese loop



(/u/DaddyMonkey)

42mm Space Grey Sport with classic buckle



(/u/inlovewithpbj)

42mm Space Grey sport



(/u/maxeljulio - 155mm wrist)

42mm space grey with black leather loop



(/u/IndianaP0wns - 170mm wrist)

42mm space grey



(/u/Hairelam)

42mm space grey



(/u/Boston_TD_Party)

42mm Space Grey sport



(/u/zinterz)

SG sport with blue leather band



(/u/zinterz)

42mm space grey with milanese loop



(/u/flamepants)

42mm space grey with milanese loop



(/u/donnierobs)

42mm space grey sport



(/u/cornhusker10)

42mm space grey sport



(/u/timeisinfinite - 205mm wrist)

42mm space grey sport



(/u/jaybird8491 - 185-190mm wrist)

42mm space grey sport, 42mm SS with link band, 38mm SS with link band



(/u/biscuitswithoutgravy)

42mm space grey sport



(/u/rrodr170)

42mm space grey sport beside Pebble steel



(/u/Rizin)

42mm Space Grey with brown leather loop



(/u/chasem13 - 170mm wrist)

42mm Space Grey with stone leather loop



 Watch (Stainless Steel)

(/u/chasem13 - 170mm wrist)

42mm Stainless steel with Milanese Loop Top



(/u/tcox)

42mm Stainless steel with Milanese Loop compared to original Pebble



(/u/PrestoMovie)

42mm Stainless steel with brown leather loop + SS with link bracelet



(/u/Naiynol)

42mm (?) Stainless steel and Sport models compared, both with milanese loop



(/u/iAmManny74)

42mm Stainless steel with classic buckle



(/u/nocharge4u - 190.5mm wrist)

42mm Stainless steel with classic buckle



(/u/Evilkevin22)

42mm Stainless steel with milanese



(/u/Evilkevin22)

38mm Stainless steel with milanese loop



(/u/skepticalchameleon - 137mm wrist)

42mm Stainless steel with milanese loop



(/u/25donutz - 205mm wrist)

42mm Stainless steel classic buckle beside Pebble Steel



(/u/jamchampnate - 165mm)

42mm Stainless steel with milanese loop



(/u/cbwyatt - 177mm wrist)

38mm Stainless steel with milanese loop beside Rolex Submariner



(/u/kappuru)

42mm Stainless steel with milanese loop



(/u/Oiggamed)

42mm Stainless steel with link bracelet



(/u/Oiggamed)

Stainless steel Apple Watch with classic buckle



(/u/Yifkong)

42mm Stainless steel with classic buckle



(/u/goldfish3037)

42mm Stainless steel with classic buckle



(/u/rfbandit)

42mm - Stainless steel with black leather loop, space grey sport, SS with classic buckle



(/u/DanceGageDance)

42mm Stainless steel with blue leather loop next to Tudor



(/u/cookingboy)

38 mm Stainless steel with milanese, 42mm Edition with blue leather, 42mm SS with steel link



(/u/lukeydukey)

38mm Stainless steel with classic buckle



(/u/applewatchtryon - 170mm wrist)

38mm Stainless steel with milanese loop



(/u/applewatchtryon - 170mm wrist)

42mm Stainless steel with stone leather loop



(/u/AdrianSilva - 155mm wrist)

38mm Stainless steel with milanese loop



(/u/AdrianSilva - 155mm wrist)

42mm Stainless steel with milanese loop



(/u/lynchjw - 165mm wrist)

38mm Stainless steel with modern (black) buckle



(/u/livelikeian)

38mm Stainless steel with modern (brown) buckle



(/u/livelikeian)

38mm Stainless steel with milanese loop



(/u/TwentyAndCounting)

38mm Stainless steel with modern (black) buckle https://dl.dropboxusercontent.com/u/7481262/Photo%20Apr%2011%2C%2012%2027%2038%20PM.jpg

(/u/TwentyAndCounting)

38mm Stainless steel with modern (black) buckle https://dl.dropboxusercontent.com/u/7481262/Photo%20Apr%2011%2C%2012%2027%2045%20PM.jpg

(/u/TwentyAndCounting)

38mm Stainless steel with modern (black) buckle



(/u/TwentyAndCounting)

38mm Stainless steel with link bracelet



(/u/slicecom)

42mm Stainless steel with link bracelet



(/u/tangoshukudai - 185mm wrist)

38mm Stainless steel with milanese



(/u/TVPaulD)

38mm Stainless steel milanese clasp



(/u/TVPaulD)

42mm Stainless steel with link bracelet next to ASUS ZenWatch



(/u/the_Ex_Lurker)

42mm Stainless steel beside original Pebble



(/u/vvcomphelpvv)

42mm Stainless steel beside Pebble Steel



(/u/metroidman)

42mm Stainless steel with black leather loop and 38mm space black SS with link band http://i.imgur.com/iIPF2DW.jpg

(/u/scennett)

42mm Stainless steel with link band - links being adjusted



(/u/chasem13 - 170mm wrist)

42mm Stainless steel with black sport band



(/u/chasem13 - 170mm wrist)

42mm Stainless steel with classic buckle



(/u/chasem13 - 170mm wrist)

42mm Stainless steel beside Moto360



(/u/The1manpack)

42mm Stainless steel with link band - links being adjusted



 Watch (Space Black)

(/u/chasem13 - 170mm wrist)

42mm Space Black Stainless steel with black link band



(/u/dluby - 200-205mm wrist)

SS space black with black link band



(/u/adeze)

42mm Steel space black with black link band



(/u/S3AN10)

38mm Space Black steel with black link band



(/u/AGIANTSMURF - 160mm wrist)

42mm Space black Stainless steel with black link band



(/u/PeterLovesMusic - 175-180mm wrist)

42mm SS with black leather loop and 38mm space black Stainless steel with link band http://i.imgur.com/iIPF2DW.jpg

(/u/scennett)

 Watch Edition

42mm Edition with white sport band



(/u/deer_with_no_eyes)

42mm Edition



(/u/MrMewlePants - 170mm wrist)

38 mm SS with milanese, 42mm Edition with blue leather, 42mm SS with steel link http://imgur.com/oW5Mx1P

(/u/lukeydukey)

Various  Watch models compared to other watches and smart watches

42mm Apple Watch vs Moto360



(/u/The1manpack)

42mm Stainless steel with link bracelet vs ASUS ZenWatch



(/u/the_Ex_Lurker)

42mm Apple Watch vs original Pebble



(/u/vvcomphelpvv)

42mm Stainless steel vs Pebble Steel



(/u/metroidman)

42mm Steel Apple Watch with blue leather loop next to Tudor



(/u/cookingboy)

38mm Apple Watch with milanese loop vs Rolex Submariner



(/u/kappuru)

42mm Apple Watch steel classic buckle vs Pebble Steel



(/u/jamchampnate - 165mm)

42mm Apple Watch steel with Milanese Loop vs original Pebble



(/u/PrestoMovie)

42mm Space Grey Apple Watch sport vs Pebble steel



(/u/Rizin)

I opted to leave out some "try-on" examples, such as the Karl Lagerfield gold band version. If there are any others that I missed, feel free to add and I'll edit them in.

Edit 3-ish: Now sorted by model