This super easy project works best if you have a phone with a battery door, but you can use a phone case too :)
Gather some stickers, I just had a few laying around my house in addition to some I bought with this project in mind.
Put them on however you like, I used the battery door of my phone because its easier remove and then put back, if you use the battery door you can fold the corners of the stickers into the inside of the case so that they stay put. (if that makes sense)
Apply clear nail polish thoroughly over top to insure that the stickers don't peel off easily. (I just had nail hardener laying around, and that works just as well too) let it dry for a little bit before you try to put it back on. If you don't want it to be permanent you can skip this step.
And you've got your final product (: