South Houston.
One of my all-time favorite bathroom walls.

Children's Aid Society.

Tequilaville.

Runners.
Thanks, Kate M.

Mayer's Tavern (Cape May).
This is one of the most specific (and frighteningly worded) signs I've seen. Click for a closer look. Thanks, Dan.

Caio for Now.
Thanks, Kate M.

Googie's Lounge (The Living Room).
Thanks, Kate M.

Rodman's.

Grand Central Terminal.

Hachi.
Thanks, Kate M.

Fornino.
Thanks, SJS - dig the wallpaper.

Sahara Hotel & Casino.

La Dolce Vita (Corolla).
Thanks, Todd - love the specificity of this one.

Battista's Hole In The Wall Italian Restaurant.
No sign at the sink, but this was beside the urinals - a nice touch.