Emojis are normally used inlined in text. So, I think, they should demo theirs the same size as they would be when inlined in text. Otherwise hard to tell tell the emoji quality.
I'm also a bit concerned with the thick black outlines, they may look not as good at the small scale (may look too noisy or may overpower small color details).
At least the lines aren't as horribly thick as Microsoft's current emoji set. Though I think they're gonna be redoing all their emojis with a 3D art style soon
