Can signs help service workers coax a larger tip?

If you're one of those people who tosses your extra coins into the tip jar after you've purchased an overpriced cup of coffee, how do you make that decision?

Two photos that arrived here at Pink, Inc., world headquarters this week suggest that counter workers are deploying a variety of sign-based strategies to wangle your small change.

Reader VZ sends this funny (but not especially emotionally intelligent) example:

Meanwhile, Mike Brice sends this less funny (but more emotionally intelligent) specimen:

Which, if either, is more effective?

(UPDATE: In the Comments, Austin Kleon offers another brilliant example).