The shower shelf eventually required further intervention. I went roaming around the house wondering what I had that would look better than the little black lantern, and eventually settled on a lovely crystal vase that was a wedding gift, and which had been insufficiently used over the years:
Pay no attention to the paint job on the walls, please. That is my fault for trying to do the edge with painter's tape instead of just free-handing. Feh. It will get fixed eventually.
The vase looked very nice - sparkly! - but a vase really needs to have something IN it. I don't as a rule do cut flowers, and whatever I did use would have to stand up to big temperature swings as well as occasional extreme humidity.
I could have used the handful of glass cocktail swizzles that we got in Mexico on the same trip that produced the mirror, but cocktail swizzles didn't seem like quite the right choice for my bathroom. Also, the swizzles each had a blown-glass animal at the end, all in different colors - they would have competed with the mirror.
I settled on a beaded bouquet.
This project had three requirements. It had to have dangles; it had to have a bouquet-like shape; and it had to not fight with the mirror and the chandelier crystals.
A friend and I went to a craft store and while I didn't find the first thing I had in mind - chopstick-like hair sticks, which come with the end drilled to insert an eyepin - I found three metal hair bands that I thought would work. I took them home and cut each one in half.
Then I cleaned up some reclaimed dangles from a cheap old chandelier that committed suicide, and rummaged through my hoard for more supplies.
The vase is half-filled with random beads from the hoard, and then I fed it a handful of long glass tubes that I acquired somewhere. I slid the hair-band ends down six of the tubes, which helped keep them stable and separated, and helped support the weight of the beaded dangles.
This is probably not the final version, but I'm quite satisfied with it for the investment. Hair-bands: $16; other ingredients: already in the hoard; and the project took about an hour altogether.
Non-trivially: everything is washable!