We completely re-painted all our rooms, and have found that instead of being "locked into" themes and uses, people have really appreciated the new environment.
We mainly used biblical themes for our rooms ---with a couple of exceptions, so the rooms work well for many programs.
For instance, in Lent we did a Journey to Jerusalem and re-enacted the events of Holy Week in the various rooms. During Advent we photographed the Christmas story using a couple of the rooms as backdrops. The key is to let them see the difference the transformation can make.
We used latex satin gloss paint for most of our murals - some on cement block, and others on drywall. They can easily be painted over when and if necessary.
Paint is not nearly as permanent as some committees would have us believe!