I have a suggestion, and I've rounded up ideas from others to inspire you!
Comic Book Hearts
To make these Valentine's Cards for friends I used: old comic books and a Marvel Previews catalog, a pack of $1 glitter cut-out hearts I picked up at the craft store, and Mod Podge. The hardest part of this craft was finding the right panels in the comics.
The glitter heart pack came with different sizes, so I used a smaller heart to trace the pattern on to the comics. I pasted the comic hearts down with Mod Podge and after they dried, I wrote my message on the back. You could do this with construction paper, too! Personalized, easy, and done.
Follow the link to learn how to make cute, geeky, and practical Valentine's Day cards from justJENN. They're great for kids and adults.
Like 8-bit and pixels and have patience for paper crafts? Then head over to minieco to get templates and instructions to make these charming pop-up Valentine's cards.
Know some images from fandom that would make the perfect Valentine? You can use Photoshop (or a free program like Gimp) to make some magic, and How-To Geek gives you all the tips and tricks in their Valentine's Day card tutorial.
Have you made your own cards? Share links in the comments!