Julie,
Show Photography isn't for everyone. If it were, there would be a lot more Show Photographers. It's difficult to shoot and the backend fullfilment process is laborious if you don't have other people to help.

Your comment about dog/people sizes is right on: the #1 Great Dane in the country, Sandor, is shown by a gentleman who is 5'7" and he kneels for photos. Makes Sandor, who is not a massive Dane, look huge.

Julie, I've seen your images -- you are artistic by nature if not by profession.

The horse venue has great potential. A good friend of ours owns/exhibits Quarter Horses in Michigan and she's been trying to get us involved in Horse Photography. Like you, I'm comfortable with dogs but don't really have a lot of experience with horses. I can shoot them moving but have no idea how they should be set up for formals. Yes, I could learn but I'm more comfortable with the things I know than trying to learn new subject matter and a new market.

Personally, I think the pet portrait business has the greatest potential.

Jim