Have you ever shopped at Once Upon a Child? They have a store in Enfield (they're a nationwide franchise operation, but the closest to us is Enfield) and they get buy and sell great "gently-used" and new items at fantastic prices.
Also, my brother and his wife did a great room for their son by ordering one of those wall murals. You walk into my nephew's room, and it feels like you're on the pitcher's mound in a minor league baseball stadium. So much fun and the prices are coming WAY down. This site has some great idea starters and the prices vary: http://muralsuperstore.com/kids_murals.htm
I would try to avoid any theme character, because he might like Elmo now, but in a couple of years that is going to feel like he's outgrown it again. You can always do things like paint the walls in primary colors of Red, Blue and Yellow, and then switch the themes to the bedspread to match his changing and growing tastes.
Ultimately, if you're planning on staying in the new place for a long time, try to picture what his needs are going to be in ten years. Is he still going to want to sleep in a race car bed or is he going to think that is too childish? How about the dresser that is shaped to match?
Another thought for you... drive down to New Haven and go to Ikea. They have GREAT kids room ideas and the prices are FANTASTIC!!!
Have fun!