Construction, 'cause that's what my DS's room is
I just got some fabric and made his curtains. Home Interiors sells construction Wallies, they're wallpaper cut-outs, a whole bunch of them for $20. If you're moving to an apartment and can't do anything permanent, you can stick them on with craft glue (which is what I had to do because the wallpaper adhesive wouldn't stick to the orange peel texturing on his walls).
Oh, and JcPenny sells construction-themed bedding, I don't know if he's getting a twin bed or a toddler bed, but the twin-size bedding isn't really that terribly expensive.