"The bartender is working for tips" works for me.
bro, tip the bartender for me.
If there needs to be a sign I prefer simple and polite like "Gratuities are appreciated"
Very gauche.......
A friend of my Mom has agreed to bartend at my wedding free of charge. We of course will be tipping her for her service, but I'd like to find a witty saying or something to go on a tip jar for our guests to tip her as well.
The funnier, the better! (Preferable "clean" funny, as it is a family function).