Poster locking

What would be nice to see is if there was a means to lock a posters stretch size. For example, say you have a texture you want to use, like a tile texture on a wall, when you go to stretch the size of the poster out, you get an over or under stretched poster and say it was tile, the tile lines don't line up. If you could set a lock in the poster you could circumvent this problem and then not have to modify your texture packs.