We too did a Toy Story room after it wasn't super popular anymore in stores. I actually ended up finding a comforter at our local thrift store with Buzz on one side and Woody on the other. We did solid color sheets. Ebay did have a lot of options though too if you searched - some full sets, some partial. We did the comforter and then got some solid toss pillows - Orange and lime green, I did the accessories in the room with fun solid bright colors (purples, red, navy etc) and got those character cling stickers to go on the walls and on his headboard, ceiling fan, closet, dresser etc, so that when we were done with that character set, I could just peel them down. I did find a cool retro-looking glass table with a lamp in it at Slumberland Clearance as well as a red rocketship nightlight. Ikea had a moon and star wall nightlight set too, that kind of also became wall art along with a planets and rocket mobile (all pretty low priced at Ikea). All in all, it turned out really cute without having to spend a ton, and now that we are onto Cars, it ws just swapping out the stickers and a new blanket to switch it around. For boys, keeping the solid bright colors will go with just about any character set up they decide they need that year, and will grow with them when the character obsession is done. We got those fabric storage drawers etc, CD holders - those were all just solid colors.
Hope that helps you out!!