Adventurer's Project Sinage

Adventurer's Project is starting to need some event signage.  My idea is that we'll need 4 pieces of ply, 2x4's and some hinges (I don't know what width yet) to make something like 2 A-frame signs.  Now what my idea goes on to say is that our most common message will be painted on them.  As for anything else, the signs could be the same dimensions as a twin size mattress.  And that somehow we could use a fitted sheet with a screen printed image for other messages?