Hmmm.. yeah I'd suggest some wallpaper, but I'm not sure how that would help with the ceiling issue. I'm not really sure what you could do to stop him from doing that. Do you ever take him out? Maybe letting him out of the cage and letting him wander a bit will help? (that's if you have a safe, clean place for that.) If you come up with a solution let me know, as I'd be interested to hear for future reference. I have three baby tomato frogs atm and any info is good info.

Edit: Maybe a bigger tank would be a solution, too. A 40 Gallon or so.. it might be telling you it wants some more room.