Don't spit slogans.

This sentence has been concise. If you change the sentence slightly, you may not be able to convey the meaning. I suggest you work harder on the design (cartoon) and color of the signboard, and make it cute and cartoon, not stiff.

If you have to change the text, "make your phlegm as elegant as talking" and "you are so beautiful! Don't spit everywhere, it will ruin your image! "