In selling market, to make yourself known, you must to:
1) know very well your product's destination (in your case learn all you can about Guinea Pigs)
2) know very well your customer types (see few statistics about Guinea Pigs owners: mens, womans, kids, how hard is to grow a such pet)
3) Guinea Pigs live about 10 years if they are kept in good heart (use that in a fancy way to convince you customers that you products may extend the life and well being of their pets.
4) know your competition, and learn from their (also from their mistakes)
5) be innovative and original (if you have already some guinea pig accessories, you can tell yourself how can be made better with less money). You can try some homemade toys or accessories, or even try to modify what you already have, "in a new light".
6) meet your potential customers on forums and clubs.
7) ask vets opinions about guinea pig's life style and health, and try to tune your products in those directions
8) try to figure that are some types of breeders that may have not a lot time to sher with pets, so they want a "simple" way to keep a pet. Here, imagine a product like aquarium where fish have all they need to live, with minimul interactions.
9) you can include in your products some gadgets to, kids love it, but also can be expensive (here you can check China's way -online- because is cheeper): autofeeders, weather mine-stations, etc.