Here is the design I came up with for character portraits for documents and dairy entrees.
1) Lorewise, every person in this fantasy world has a unique set of stamps that they use for their documents and dairy entrees (Including Mayfly herself). This is to help immediately orient the reader to have know who wrote it and the tone it should be read.
2) Portraits are only allowed to be 2 tones, and should look like they would make good designs for a shirt.
3) Below the portrait part of the stamp should be a demons symbol. A demon's symbol is an image of the physical trait that the type of demon they are is as it appears on their body. So, for example, Mayfly is a Glasswing, so under her portrait is an image of what the shape of her glass-wing-bit looks like.
Leave your thoughts in the comments if you'd like to!