This graffiti can randomize depending on what I assume is RNG. As user Regret today has noticed it seems to just be purely random. So you might just have to comb the entire casino depending on when you look.
I've only found it on the wall once. I almost always find it behind the castle upon one of the towers. You can grab a Balloon with
and float up to the top of the castle to locate the graffiti. When you're close enough you will lock onto ithttps://gamerdvr.com/gamer/new-paralyzer/screenshot/15633835
Kitty Skies claims also on there's the sticker inbetween the stalls to your left as you enter.
There seems to be more Sticker locations possible than I originally thought. People in the comments sections have been stumbling across more.
The sticker jumps around however so if you can't find it eventually it will show in our known locations
It seems there's more locations than I initially thought. Check the comments. This sticker moves.