Nobody is going to spend money for those stickers. They are cool, but you forget that you are advertising mostly to kids and young adults that dont have jobs. And if they do have a job, they are spending all their money on weed and booze.
I think you should just give them away. The more they are out there the more potential traffic to UPL.
Now that I have made you realize that your plan to become rich off selling stickers will fail.... GIMME A STICKER. <3