Hello,warrior here!First of all, how did you do this in Gimp?! That's such a confusing program to use (I use medibang), and it looks wonderful.The red of his hair really pops out, and the other colors used on him look very realistic. However, there is some stuff that could use improvement: AnatomyI saw the traditional sketch you did, and the first thing I noticed were the eyes, or the actual glasses to be precise. You can see that the glasses are uneven; one lense is smaller than the other, and the eyes don't look correct on his face. They look a bit too simple as well, and his eyebrows and facial hair are a bit too solid and messy. I understand in the photo that his glasses are slightly askew, but that shouldn't change the size of both lens. I think that it might've been easier to put your reference photo on a layer and then put a slightly transparent layer (change the opacity of the actual layer, not the brush you're using) and then pretty much block in the rest of his face while adding other details. This would help a bunch if you could do it with other people as well to get realistic practice in, and I'd suggest Jack and/or Felix for that type of practice. (The gamer trio! :3) Background/Other stylesThe way you mimicked the other styles was very accurate, so good job on that! Although you had to do it in a 2D drawing, the top left drawing of him looks surprisingly accurate to the animated style. I don't have much to say on the other drawings, I think it might've been better if you drew them in different poses than those in the actual videos. I think you'd be up for the challenge, and it'd be really cute to see them interacting with each other. The background looks... rushed, in a way. I wished you could have painted the background of the reference as well, because the pink and red seem to clash against each other. The pink just doesn't really suit the artwork. Other stuff!(wow, isn't that precise? XDD)I started focusing on the colors, and I realized his skin looks a little grey. You might want to go a bit on the yellow side, because he looks a bit ashen compared to his normal, healthier looking skin in the photo. The shading on this is also a bit lackluster, but it might just seem like that because there isn't any lineart. I'd suggest looking at makeup contour pictures to see where you should and shouldn't shade the face as well. The last thing I noticed after going back and looking at the piece again was that the red hair actually looked too realistic compared to everything else, which looked a bit flat. You might want to add texture to the rest of his hair, along with making the shading on his skin a bit more noticeable.Despite all of this, it's still refined and finished off. I've seen some paintings where you can still see the sketch, and I'm really happy that this one doesn't have any lines visible because it could've made it look bad due to the smooth colorings, and if you used black it would've been WAY too harsh. I'm jealous because I could never draw something like this in the most confusing art program ever (heck, I can't draw something like this in medibang either xD). Hopefully my critique helped you, and thank you for drawing more fanart of Mark! He's such a sweetheart, haha ^^ Hopefully I'll see your art later in Project Comment!