The instructions below I pasted in verbatim from the design*sponge post, here. Let me know if you try it, and how it turns out!
"Here’s what you’ll need:
-- 9” x 12” piece of cardboard -- 9” x 12” piece of wallpaper or other decorative paper -- rubber cement -- x-acto blade or scissors -- clear contact paper -- large bulldog clip -- dry-erase pen(card used in the picture above is from something’s hiding in here)
1. apply rubber cement to the back of your wallpaper and to one side of your cardboard. adhere the paper to the cardboard, smoothing out air bubbles as you go.
2. if desired, round the corners or cut your cardboard into a decorative shape using an x-acto blade or scissors.
3. cut a piece of clear contact paper that is slightly larger than your cardboard, and apply over the wallpaper."