I've made PDFs available through Google Docs, in two versions: one suitable for all ages, and a slightly saucier version. If you'd prefer to express your affection digitally, grab them individually from Flickr: they're divided into nice and naughty sets.
Here are previews of the three designs:
Dromaeosaurus and Camarasaurus...
and Carnotaurus and Triceratops.
Yeah, yeah, the pairings aren't strictly accurate, time- and place-wise. They're valentines, not posters for SVP. Show the object of your affection your feelings and share your affection for dinosaurs at the same time. It's efficient!
If you like these, thank Jennie. Not only was it her idea in the first, she helped me pick out the "naughty" caption for the Troodons when I was hopelessly stumped and thinking about ditching the naughty version completely.