My first helmet was a petzl ecrin roc .. it has stickers from gearexpress.com, grivel north america, and probably some other crap. I just keep it in my closet as a spare these days, since it's getting on in years.
I bought a petzl elios later on, and just put a small julbo sticker on the back .. mostly to prevent confusion in case I happened to climb with someone who also wore a blue elios
Some of my climbing partners don't bother with stickers. A few have really colorful ones -
My latest ecrin roc is completely blank. I should probably throw something on it because one of my other ice partners has a similar blank ecrin roc ..
What stickers do you have on your climbing helmet, if any ?