Actually, they make little baby tiaras that may fit around the head tube, that's where I'd put one, but I wear one of the regular ones around the house every once in a while. Fixes a sad head. Besides, it'd be tough to clean. Just pack the attitude.
And Irulan, I live in New Orleans. I have a special Mardi Gras day helmet with ostrich plumes and sparkly stuff, rhinestones, diffraction stickers, it's a diadem/ noggin crash pad all in one. Actually, the body glitter only comes out a few days a season, I like flower and butterfly clothes for the daily grind too. But some days are special, you can feel it.