A better person or not, this sign from the Uffizi Gallery in Florence will make you a bit more cultural, even if all the great Art in the gallery fails to accomplish it.
What puzzles me, is why the sign is just in Enlish and Italian? I believe it begs to be expanded to include other cultures. I feel somehow… left out, as a Russian.
My xenophobic ideas:
Russian: Visitors are kindly requested not to drink vodka and let their bears off the leash!
Chinese: Please remeber that blocking the view of an artwork while taking photographs of each one by everyone else in your group may interfere with other visitors’ plans for the rest of the day.
French: Visitors are kindly requested not to throw angry looks at people taking pictures of each other, throwing chewing gum on the floor or drinking vodka.
Any other rude and xenophobic suggestions? )
Standing Ovation, Seated 
Americans: Please do not be as loud as usual, it disturbs other patrons. Also, mind your fanny packs/souvenir hats as they may injure the previously mentioned patrons.
Thank you! The souvenir hats are an amazing observation )
I was born and raised in the former USSR so I may add to this Russian xenophobic suggestion:
“No fighting! / Не драться!” 🙂
No fighting after vodka. I like it. Спасибо!
Even better! Пожалуйста 🙂