I'm not sure there are any specific idioms -- I think you might be wanting slogans or mottos instead.
litter
were bitter about litter
No slogans in chemistry !
horsey (in high pitched voice)
mile high city!
litter
were bitter about litter
Do not litter!! Use bins!
Fnevvy
Cleanliness is health
ritans paradise
"Do it again in 2010."
Class of Swag16!
No slogans in chemistry !
horsey (in high pitched voice)
mad river is mad
Customer First