Currently the only use for them is to add in your house as a cosmetic addition.
Suggestion:
1. Add the ability to sell them to a slayer master for slayer points and(or) GP.
2. Not sure if its possible but maybe add a way to gamble them like we do with firecape for a chance of obtaining the pet from that boss?
^ maybe a decemt chance of obtaining pet, like 1/50 or something, cus its as rare as a rare drop