Emotes.

Every emote name starts with your channel code, the first five letters of your channel name, so the whole name reads like :yourcodeHype: in chat. Letters, numbers and underscores. PNG, JPG or WEBP up to 512 KB (resized to 128 px automatically), or an animated GIF up to 1 MB. Animated emotes are a partner and affiliate perk — 3 for affiliates, 6 for partners — and each one counts against that allowance instead of being resized.