This is pretty self explanatory if you have used Discord. Allowing for custom emojis, and stickers would make chatting within second life more enjoyable. Link previews would also be a welcomed addition. This could also incentivize more paid memberships.
Custom Emojis, and Stickers can be tied to a users premium/paid membership status, allowing for more depending on membership level. Members at a certain level should also have the ability to add custom emojis and stickers to an SL group, allowing them to be shared among group members.