This discussion began many years ago, and unfortunately still seems pertinent today. As you will read, "Getting Permission" to do some painting is difficult in some churches. What you will also read is how some creative educators have not only come up with creative workarounds, but have come up with ways to bring "permission givers" onboard.
The "Workshop" descriptions and design ideas here at Rotation.org have a lot of "classroom décor workarounds" for churches where permission is difficult, walls are off-limits, or where space is shared.
My teachers and I think Rotation means (gasp!) colorful inviting space for kids!! So when our church recently expanded, we wanted to paint our new classrooms with colors and murals. The problem is that an "Interior Design Committee" was formed to make decisions about this new space -- which INCLUDED our new Sunday School rooms, were very concerned that this new space blend with the old space (i.e. white walls, white doors, white...) No one on this committee had children in Sunday School, though some are supportive of the program.
So we're stuck with white walls, and the need to "ask permission" for anything we want to put on the walls, ...paint, decor, posters, you name it.