How about a diamond fold card?
You could do it in a blue CS with the white ribbon in the middle and hang a rhinestone charm in the middle. Then put the invite info on the back...
here's a link to a tutorial.
You can layer the square in the middle and pop it up with thin foam squares
http://www.youtube.com/watch?v=hkDfbyHXKvY
I recently made this fold.
I just added two pieces to each side so that the closed card would be bigger.