Stickers are awesome - everyone loves stickers! For HIBP's 5th birthday I'm getting a bunch of them made and giving everyone else the artwork so they can have their own printed. You're welcome to take this artwork and use it with the likes of Sticker Mule (that referral link will get you $10 off and give me $10 towards my next order) or anywhere else, for that matter.
Do also feel free to submit your own to this repository. I welcome any other creative content that you think others might benefit from. Vector graphics are awesome, but submit a PNG too if you can so that everyone can see what it looks like.