It sounds like a recipe for selective enforcement. You may think you have a team culture that can be chill about this sort of thing, but it only takes one complaint to HR -- or to Twitter -- to retroactively turn your cartoon butt into a symptom of a hostile work environment.
They're definitely not appropriate for all workplaces, but for small, more informal teams, this sort of thing can help build a culture and encourage teamwork.
It really depends on the company and unit culture.