I give these to students to glue in their textbook. If I need to give a reward or incentive to complete their work (without relying on candy all the time) I give them a sticker or stamp on this sheet.

Every 3-5 stickers they can receive a small prize (coupon for the school stationery store, candy, pencil). I initial the sheet when they've received the prize.

I teach middle school but I think they are good for elementary too.

Themes:
Super Mario
Pokemon
Harry Potter
Kakao Talk

I needed to make the circles bigger for the stamp we use so I combined the previous two posters ideas.