First of all: I'm no artist. But if I had made that background, I would have tried to make the tiles a bit less repetitive. Mainly the platform tiles, but also at the back wall. If you are not using some kind of tile script to save space or increase performance, I would not recommend copy-pasting tiles since it tends to look like a pattern.
Also, I think I would have toned down the black and white tape at the edge of the platform a bit.
About the portrait: Again, I'm no artist but whenever I try to do artwork, it ends up with too little contrast. I believe this portrait suffers from the same problem. It would benefit from more shadows and contrast. Look at reference photos and other peoples artwork for inspiration.
Hope it helped. At least it's on topic.