preserving dead pets just isn't my thing in general.. granted, they're beautiful in a different way than say, a dog, but it still just gives me the willies. With hunting mounts, you didn't have any sort of attachment to that animal other than the tasty steaks you made last night... when its your pet, i feel like every time i looked i'd just feel bad that it wasn't still alive.
If ti's a fish I was attached to I store them there until I can bury them. Otherwise I store them there until trash day. I couldn't stand to throw a fish I'd really cared about for years into the trash.