Split down the middle, no less.
I appreciate all the replies and the suggestions. I’m torn because I most appreciate it being esoteric. While at the same time I find myself wanting to make the joke as accessible as possible. It’s a fools errand, indeed. This image is very similar to the one I’m using: https://wallpapers.com/images/hd/uranus-2500-x-1667-picture-1mo1jqjbwyvv8kwm.jpg
I’ve enjoyed the thought experiment, as it were. But mostly I’ve enjoyed the laughs today.
And @Ponderoid… that Uranus split between 2 pages of the book. 
That just can’t be real?
I think you should leave it for the lucky few to figure it out. They’ll feel so smart when they do.
How about one of those “maps” of the solar system, the ones that show planets in rings. Then add a “You are here” arrow pointing to Uranus.
That’s as close to perfect as you’re likely to get.
That image is perfect. The novelty of the vertical rings is enough for a curious visitor to ask what planet is in the bathroom and you can answer “Uranus”.
Yeah. I just about can’t imagine a better image for the OP’s purposes. But it has been a fun thread nevertheless.
I’m sure this exchange has happened in Scotland at some point.
“Uranus!”
“And you’re Angus!”
Like the joke about the Scotsman celebrating Purim that ends with the punchline “It’s me and MacGregor!” .
So, the astronomy club at my school had its first meeting today, and my student leader assured me that she had everything ready: A slideshow on the history of astronomy, and some astronomy-related coloring sheets. The coloring sheets featured the Sun, the Moon, the Earth, an astronaut standing on the Moon next to some instruments, and… Uranus, and no other planets. Which she openly acknowledged that she included just because she has an immature sense of humor.
She’d fit in great here. Once she turns 13 and we let her in.
I teach high school. All of my students are over 13, and she’s 17 or 18.
And yes, high-schoolers do like coloring.
Apparently not, if we’re to believe the OP. But of the images proposed, I think your last one is the best. Blue, small thin ring. That’s about as “iconic” as it gets for that particular planet.
I’d go with something like this. You don’t want to title it “Uranus”—too obvious. But, prompt guests to figure out the 7th planet, then they’ll get the joke:
