Emotes are depicted as characters in the Emotes tab. One character is a man in full white armour with a white medium helmet, another character is a man in a default outfit with brown hair, another character being a woman seemingly wearing a blue dwarf shirt and skirt, one is a jester (as in the Neitiznot jester outfit), Romeo, a cave goblin, a mime, a woman with a bronze platebody and a dragon plateskirt, a zombie, and a skillcape-wearer.
To make it easier to see a dark emoticon clearly for those that use dark backgrounds such as via Theater Mode, you could create a thin 1 pixel line of off-white (#F1F1F1 is the correct color code) around the edge of the emoticon shape. The reason for this specific suggestion is that this is the default background color of Twitch chat, so the outline will not be noticeable outside of any dark mode. This is not always necessary though, so use your own judgment and test it on a dark background to ensure quality.