Hmm...
Kind of cheesy, but last Valentine's Day, I made him a cake in the shape of a mustache and beard (since he's super into beards) and some bacon roses. Not really "romantic," but it was over the top since he wasn't expecting it and it took almost all day to make them.
Other than that, just planning surprises for him. I try to randomly pick a restaurant I think he'll enjoy and surprise him by going there.
Oh, and car parts. He loves being surprised with car parts, but I do too!