I have written graffitti on many, many walls of these things. The "Mexican Space Shuttle" was a fan favorite years ago. I also write:
*Don't eat the piss mint.
*Watch your toes, I cut the hose.
*This toilet paper is like John Wayne...Its rough and tough and won't take **** of of anyone.
*This place smells like my Uncles Meth Lab.
*Shaking your **** more than 3 times is considered masturbation and is not advised in this toilet.
*(Over the piss bucket) "KJs Hard Hat".