Creative Finishing (interior) Techniques?

I'm considering abandoning my plan to use 3/4" oak plywood for my side walls. It's pretty expensive ($118 / 4x10 sheet) and the exterior is just going to be painted anyway. I can get a 4x10 sheet of ACX ply for about 1/2 the price of the oak. It would probably need some filling and sanding on the "C" side to get a nice smooth surface, but if I can come up with a neat (and somewhat simple) way to paint the interior, I think I'll be just as happy.
So... ideas? How-to's? I was thinking sponging or textures of some sort, but have no experience in the such.
So... ideas? How-to's? I was thinking sponging or textures of some sort, but have no experience in the such.