You probably won't know what you're working with until you actually get inside the room his first day on campus. Once inside, try moving things in different places, along with his roommate if he has one. Depending on the space and personalities, it might be better to divide the room into "sleeping" and "studying" areas, or to divide it into "yours" and "mine" areas. If he doesn't have a lot of hanging clothes, you can save space by putting the dresser in the closet. When sharing a closet, consider purchasing shelves and dividers to go inside.
He might think that asking his new roommate what color bedding he's bringing is probably the lamest question ever, but a bit of coordination doesn't hurt. At the very least, they can decide who's going to bring things that they can share, like the television, dorm refrigerator or video game console. You might also be able to suss out any decorating ideas that might be a point of contention. Choosing to decorate with your son's favorite team emblazoned everywhere might cause a problem if that team is the rival of his roommate's favorite team.
Most dorm rooms start with institutional-white walls that are drab. You can really spruce the place up by adding color or meaning to the walls. For example, consider purchasing coordinating curtains instead of using only the dorm's window shade. Frame pictures and posters to give them a more polished look. Vinyl appliques are an easy -- and removable -- way to infuse your son's personality in the room. Choose a favorite quote and have someone custom-make it to put on the wall.
Your son has his clothes, his computer, and a blanket for his bed. He might think there's nothing else he really needs. Little touches, though, bring warmth to the room. A small lamp will likely offer better lighting than the one provided by the school. A rug with a cool design will warm up hardwood floors or cover up drab stains from years of use.