At hexbear we already have custom star trek emotes and a community for user suggested custom emojis 
Maybe you could chime in with how its organized? Ill also hop on over to see how you all do things later today :)
From a short peek at the markdown it looks like a normal picture link. Im not terribly familiar with federation, perhaps this is cause im viewing it from another instance, but i would hope for some kind of :emoji: syntax.
We do have :emoji: syntax, when I start typing after a : I get a popup of matching emojis, or I can pick from a (very long) list. They just show up as pictures for the rest of you due to federation. They're also sized more consistently for users viewing from hexbear but I hear lemmy is going to fix that for everyone soon. Our Emoji Science Officer, or perhaps People's Comissar of Emojis, is @WhyEssEff@hexbear.net she does the emotes.
On Mastodon, the tenforward.social instance where the @Admin@StarTrek.website & @ValueSubtracted@startrek.website have accounts, has its own set of emojis. Some of these seem to have been contributed by users.
It would be great if our leadership here could check in with @guinan@tenforward.social to see if she would generously share her protocol.
Come to Quark’s, Quark’s is Fun!
General off-topic chat for the crew of startrek.website. Trek-adjacent discussions, other sci-fi television, navigating the Fediverse, server meta (within reason), selling expired cases of Yamok sauce, it’s all fair game.