Decorate walls!? My bedroom is on the top floor of my house and...

My bedroom is on the top floor of my house and it has angled, low ceiling. I want to decorate my walls because they are really boring. I can't sway picture frames of any other wall art on the walls because they don't stay up on the angled walls. Does anyone have any design about decorate my walls? Thank you!
Answers:    get a set of unframed small prints, similar to 7x9 and go to a frame shop and ask them to be foamcore mounted. (also call dry mounted). attach to the angled walls with a hotglue gun. i would paint the wall first within a color i like. do not try this surrounded by seattle or other humid city though because the foamcore might warp
I had like peas in a pod problem in my older apartment. I found that some retailers of frames such as myframestore.com have picture frames that come near different types of hanging trappings. I used the hanging cable and its still holding up!