Sticky? BAHAHAHA. Seriously though, have what you want. I checked with the police, there are no laws at present limiting you to x stickers on your helmet. Who knows, this could change so get as many as you can before they introduce a new law.
use a lighter to heat up the sticker, dont hold the flame on the sticker, just move the lighter back and forth enough so that the sticker warms up and you can form it