they look really cut and pasted. there needs to be more shadow and make it look like there's a single light sorce. the other thing, the perspectives dont match up. from the angle the shot of the background is taken you should be looking at the top of someone's head, rather than straight on. the stop sign just kinda ends, there needs to be a little more of a definite "here is where the stop sign goes into the ground"

if you moved the dude and the sign farther back the perspective wouldnt be an issue, and just for the sake of visual pleasing-ness i'd seperate the sign from the dude.

i love the colors you're using and the grittyness of the stop sign fits really well with the look of the piece. i also love the background, idk if you just found it but it fits really well with the feeling of the picture. the sepia-ish adds to the image and makes it feel grungy but still clean cut. i like it a lot