Use old wooden milk carton crates and paint them for your purposes. For example, if you need somewhere to put all your books, paint the crates different colors and paint your names on them. These can easily be stacked to make the most of your room space. You can also put your clothes in these so that you don't need a big dresser. If you're allowed to put nails into your walls, you can mount the crates at eye level or higher to allow for more floor space while still adding storage.
Cinder blocks were a common way to cheaply decorate your room in the 1970s, but you can still use them to hold up such things as your TV or books. The holes in cinder blocks also double as shoe compartments, so you can always have your shoes organized, leaving more room in your closet. The little compartments also hold extra handbags. Find cinder blocks at your local hardware store. Get the lightest kind because they can get very heavy. Paint them whatever color you want, but use primer first as the holes will soak up most of the paint if you don't.
Don't underestimate the power of a picture or picture frame. Instead of buying posters as many students do, make your room different by hanging pictures on the wall. Get blank wooden picture frames at a craft store and decorate them using things you already have, like scrapbooking materials, paints and markers. Add a decorative ribbon to use as the hanging strap. Then hang them using simple tacks you press into the wall.
A glass-bottle vase will brighten any room and only has to be filled once to last the whole time you are in your dorm. Find a glass bottle that appeals to you. This can be a modern glass bottle from which you remove the label, a classic glass bottle you get at a thrift store or a simple mason jar. Clean the outside of the jar and paint it. You can paint the whole thing or just add certain decorations on it. When the paint is dry, fill the bottom with rocks or glass beads and some silk flowers. This way you don't have to buy fresh flowers all the time, but they look real. If you don't mind buying fresh flowers, then just layer the bottom with glass beads and add flowers and water.