Viv backgrounds?

[Suess]

Awhile back I saw a temple themed Viv someone on here made, using styrofoam, it was beautiful. I was wondering if there is..I guess a limit to what you can do for backgrounds? I mean, do they need to stay as natural as possible or can they be anything?
I'm asking because I want to design something for my boyfriend's tank for what ever snake he brings home after the expo in Feb. And he mentioned that it'd be cute to do something Dr.Suess themed for my boy Suess, but I'm afraid that might be too un-natural.
But I don't know much about these things so I figured I'd ask.

Thanks!