Hmm... When adding the character, you should have paid more attention to layers. From her shadow it does not look like fg and bg were rendered together. She seems to hover above the grass. The genral scene is really not bad. You should tune down the bum on the big bricks a bit. It is a bit too strong like it is now. Some bushes in the background would also make it less barren and add to the look of the general vegetation. To enforce the look of the ruin, either add some plants growing up on the wall, not add some rubble and debries, depending on how old or fresh the ruin is supposed to be. I ranked this picture "good" because I think it could be much better, but it is already very interesting. I would like to see more of this and some adjustments could make it great, if not excellent. Render on! :D