Your items appeal to very small niche market of pitbull enthusiasts. Actually, it's even smaller than that, because it's pitbull enthusiasts who buy pitbull items feature pitbulls who are not their own pitbulls.
To appeal to a wider audience, your products would need to be witty and clever, not just a collection of stuff with pitbulls.
I'm totally part of the population who thinks pitbulls get a bad wrap, but I'm a pug person, and I buy novelty items with pugs on them, and my friends buy me gifts with pugs because they know I love pugs. Pugs made it to the mainstream because of the "pugs not drugs" products in Urban Outfitters and the rise of ModCloth and Winston, their pug mascot. Let me type "pugs" again. Pugs.
Your products don't have the "pugs not drugs" catchiness. However, that doesn't mean no one wants it. You should join some pitbull rescue groups on Facebook and post your items there. I'm a member of the Colorado Pug Rescue, and my fellow pug enthusiasts post stuff like this all the time, then they wear it/bring it to our meet-ups in the park and we laugh and laugh and laugh.
Also, make your photos the same size (I do 1000 px x1000 px) because your collection pages look a bit messy.