Yesterday I happened to see some images of dog breeds that have been on stamps and thought, "Why, those are quite attractive. I remember liking my bookmarks made of cat stamps. There must be many such." (cough) You think? Wait till you see the dog-stamp-collecting link I'm going to give you in a second here.
But first, did you know that the first dog on stamps was the Newfoundland, in Britain in 1887? And that subcategories (such as Dogs) of stamp collection each have their own hobbyist study unit? They're listed at the American Topical Association. (A subject, in a stamp, is called a "topic".)
But wait! You want to see beautiful dog stamps? You want to see if your dog is listed? (Ours is.) Well go here and seek alphabetically by dog.