I would like to mirror what everyone else said and say that the bridge is a really important part of this and adding variation with the bricks would help a lot. Even though it sounds like you just threw this together it already looks awesome I look forward to seeing more!
Oooh, very nice overall. Would like to point out that the bark for the tree is very obviously a lot smoother and less detailed than the texture would suggest. Making it look much less varied in depth and detail could go a long way towards selling it. I know it's not really ideal, but until you can afford half a million…