Most everything looks shockingly realistic, at least without analyzing too deeply, but the horse's tail immediately stood out as looking fake to me because of the simple brush strokes, the blue thing in the background looks like a giant crumpled paper that was colored on with a crayon, and the further background... I can't even tell what it could be. I'm currently under the impression that you weren't trying to make a perfect realistic picture, but were more interested in what you could learn from imitating the photo. Anyway, amazing job recreating the realistic looks.