Hi love the grey colour. may i suggest that you may wish to add some depth to the bridges. the back bridge you can a 3d effect on the arch on the right hand side so then it makes the bridge 3d asy you have with the front arch.



middle bridge front right hand side add some shading to the front arch where it would cast a shadow onto the back arch. Will make the front bridge pop out then.



Have you ever looked at making the trunks pop out. like your birch, but for the darker 1s add a thin light brown like where the light would reflect off the bark.the trees under the arches make some depth so it looks like it goes further back. the way i would do it is do a light green wash over what you have then paint the same again over the top of the wash, obviously not exactly on top of the 1s below. then add another wash. the first 1s will push further back. keep doing this till you are happy with the layers. it will initially feel like you are trashing the painting but it will give it depth. remember only a watery wash you dont want to completely obscure what is under the wash



do like the detail at the top of the bridge.



lighten the tone of the blue in the sky to really bring out the bridge some more and add another few speck of lighter green almost white or yellow where the light would hit onto the leaves



Hope this helps