Hi

If you google "wall murals" you'll find some that are wallpaper.

Also check out Anderson Party and Prom online. They have some 'woods,' beaches, and mountain backdrops.  Years ago I saw one HUNG from a pvc pipe like a backdrop.

Another option is "do-it-yourself" enlisting the help of artists in your congregation, or even pages from a coloring book projected onto the fabric that you have attached to a wall. You would need an overhead projector.

The advantage of recruiting artists in your church to do the drawing is that you can then have volunteers involved in doing the painting. If your artist types provide "color by number" direction, minimal art ability will be needed for the painting part.

You can make it a party, and perhaps get youth involved?

I hope that helps!
Blessings
Jan S