fix the canvas size. it's too short, height wise.
don't try to stuff your canvas full of shit. if you know how to, then you can mix 2d and 3d resources, but if you don't know how to then don't force it.
stick with one or the other until it becomes a bit more comfortable. try more natural coloring, the ones you have clash and don't work. pull from your stock image, try to work it into a more defined plane. if it's middleground, don't stamp it on because it just sticks out terribly.