I currently use nip94 to do this and there is an upload tab on Gifbuddy for users to add their own gif (which should show up almost immediately on nostr search)

The counter on the main page is logging the size of the nip94 repository for GIFs published by Gifbuddy

My first reaction is that adding a new kind would reset the progress and split the dataset, but I may be missing something

Why nip51 over nip94?

I actually already have a nostr native gif search engine that queries nip94 events, but haven’t advertised it much because the index is too small (<6,000):