Pushpins on foamboard. Trace your design first, buy twice as many pins as you think you'll need. If framing, cut foam board to frame first. - Cute way to use the push pins I bought for my DIY headboard and didn't end up using.
We've used a similar corner shelving unit to create space in a small 7 by 9 ft room. It's a great, easy shelving solution for small spaces (although installing it was a bit tricky as the walls weren't plumb.