It's nice to be included in fun things, isn't it?
Well, probably these items don't really care, lol, but they need to be included on your card:
Sticker (at least one), Ink (you can apply this anyway you want), and at least one piece of patterned paper.
Here's Mary's example
Lovely, and there's her sticker from SRM Stickers right in the middle. Love that pop of yellow she used!
You can use any theme, and any other decor as long as you include the above items in your card design.