Note this isn't a keyboard extension (yet, at least). That's what I'd originally hoped to do, but I've been told it's still not possible to make custom emojis work exactly like system emojis. But I'm continuing to look into it!
If you have suggestions for icons to add to the app, tweet them to @cheermoji, and tag @cheermoji with your coolest creations and I'll retweet the best!
If you have any bug reports, please email them to firstname.lastname@example.org.