Ooh, yeah, that can be rough. I was recently looking for a new comforter and I had the hardest time finding anything I liked even remotely in my price range. x_x If you can stand to wait until late Summer to buy one, I'd recommend doing so. Around then a lot of stores start getting "dorm stuff" for kids going off to college, so it's much easier to find cheap decor. Generally it's all very college kid-y in design, so that can be useless if that's not your style, but you can also find things in more generalized styles, like a navy comforter with no crazy pattern or something like that.

Another thing that's really helpful is to just change little things. Like a throw blanket tossed over a chair, decorative pillows, a framed print, or some cute vases. Better yet if you can find those things at a thrift store or on clearance! Those things can give just the right amount of fresh newness to make you happy when you look around without having to redecorate the whole room.

I also tend to rotate out my knick knacks a lot. I'll put whatever I don't want to use right now (but still like) on some shelves in the attic, where they're easy to see and get to. Then whenever the "AAAH GOTTA REDO EVERYTHING!" bug hits, I can just run upstairs and "shop the attic," as I call it. Take up the things I'm tired of, bring down things I haven't seen in a while to use in a fresh way. Helps to satiate the need for change without costing a dime.