'"She realized she was in a bathroom with a very large painting of a blue sailboat on the moon hanging above the toilet." Page 8, Yoshi's Paintbrush: Lessons in Nonconformity
I painted the image described in Yoshi's Paintbrush, though not with a bathroom in mind. Nevertheless, I think the swirls of the sand would complement well the curves of a toilet, and the blue is a good contrast against white. (Image above taken from my art gallery at danishpaintbrush.com)
My painting teacher, who received many artwork commissions, told me that when a client requested a painting of the sea, it was almost always meant to be placed in the bathroom. I suppose a sea of sand is close enough.
What kind of painting do you think looks good in a bathroom?