How To Store Big Paper

I love big, bright, colorful paper. Large sheets are useful as backdrops for my photos here on Cute & Useful, and they're so, so pretty to look at. The trouble is that they should lie flat, so they take up a lot of space. Then they get stuff put on top of them because they take a lot of space, then they get messed up.

I need to be able to lean them against the wall. OK. Disclaimer. I don't know what the dark-brown, heavy board I used is called, but I knew what I wanted and I asked my husband to get it...I'd like to tell you what it's called but really have no idea and Googling, for one of the few times in my life, has no answer. It is sturdy and smooth and the outside of it is a glued paper. It is inexpensive.

Here's what you do. 

1. Measure your biggest piece of paper. Add a couple inches width and height.
2. Go to the home-improvement store and get the dark-brown sheets of whatever-it-is. Ask them to cut it to your measurements if need be.
3. On your table, lay down a piece of the board, then all of your paper, then sandwich with the other piece and clip. At the moment, I'm getting away with a clip on each side near the bottom, and one on top.

I can rest my paper against the wall like this and the pieces stay flat and don't fall out the bottom. I have to pick it up and lay it flat on the table to add or remove a piece, otherwise they fall out the bottom a little. I'm not sure if I should hinge the bottom or what. I like being able to remove the top piece to get at my paper, seems like if the pieces were hinged together, it might be cumbersome. The clips are my solution so far.

Another use for this brown board is as a table protector -- one of my art teachers cut it to fit the tables and put on a new piece each semester. This way there were no worries about glue, nicks, or paint -- great idea if your dining room table doubles as an art space.

Any more suggestions? Anyone know what the board is called?