Well... the man seems to levitate (you'll need to apply a shadow that is created by the wall), there are some elements that look NPA. You'll need to work on the perspective (well my art classes were in french, so get ready), so you'll need to work on the "point de fuite" (basically the point where all the perspective lines join up). Get those things sorted out and you can start:
wall textures; anatomy correction; the hues and contrasts; light source correction.
AH and I suggest you change the time of day, it can change your scene completely ;).

Lol I'm of English descent