one last thing disturbs me: you're using plain white or plain black for some scribbling. This is a bit perplexing, as one expects limitted contrast at that distance, and other artifacts, such as chalk not being uniform in brightness on irregular concrete walls.
I also note that you use some smooth shadows around (some) crates. When doing this, make sure it's coherent with your lightsource. Esp, it's unlikely that the shadow would be only a few pixel large on the sides, but stretches far away from the base on the right. It'd be better to only enclose the base, not the whole perspective object. An excessive shadow right below a crate may also give the (false) impression that the crate is "floating over the ground". Imho, you're very close to that boundary with your metallic 9-21 thing on the right of the private eye.