I'm not sure there are any specific idioms -- I think you might be wanting slogans or mottos instead.
1) Litter is bad.
2) Don't let pollution win!
3) Put cho' litter in the bin yo crazy fool!
=] hope you like!
"Give a hoot - don't pollute!"
plant trees, save life!
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
What element do you have
Class of Swag16!
"Do it again in 2010."
ritans paradise
No slogans in chemistry !
Customer First
say what you think