Looking good Sera-H.

This is just a suggestion though, but you might want to put some variety into the building placement, shapes and colors (and if already working on that, please ignore my last.)

I would also think about putting a semi transparent layer of dark green under your trees to bring them a bit more unity...

I know this is a bit late and Rav has already taken care of the problem, but what I did to make the base picture larger and higher res was to up the scale; the original was at 1000px by something so I put it at 3000px by whatever the ration gave me, and also raised the resolution from 150 to 300. This made things a bit blurry though (which I didn't notice until later) but gave me a larger picture to work with.

Hope that helps in the future...

now to actually get some work done on mine ...