For ID purposes, an image/design may actually work better than a bunch of numbers or letters. It depends whether you're intending the tattoo to supply some kind of contact information, or to prove ownership if there's ever a question of whose dog it is. Numbers are easily altered (3s become 8s, etc) as are letters. Ear tattoos can be cut off. Chips can be cut out. It would be really hard to alter an image without leaving evidence of the original design. I could see having a design tattoo for a dog of a breed where they all look pretty similar to each other. My zois are very distinct as individuals. But if they were labs, or dobes, or rotties, or any other breed where one looks like the other to Joe Schmoe I'd consider it as a backup form of ID. With a pack of hounds I'd understand them all tattooed with the same design in case one got lost while out hunting, especially in an area where theft is a possibility. A tattoo is a tattoo, and I'd probably opt for something nice like a stylized chrysanthemum vs. black dashes or random (to other people) numbers, etc. There's the option of freeze branding, but it doesn't work on white dogs. Also, I think I'd prefer a cute discreet tummy tattoo over giant white numbers or designs in my dog's coat. Also, branding seems like it would be a lot more painful during the healing process than a tattoo. Anyway, I probably would never do it. But it doesn't bug me. Cropping has a waaay longer recovery time than a tattoo and that doesn't really bug me either. With all the dogs cats who don't even get basic care, I'm not going to fuss if someone tattoos their animal. The animal doesn't care if they have a tattoo.