I was researching creatures from Dungeon Crawl Stone Soup and noticed that they use numbers for their various demons, and I thought that numbers for demons would be a good idea to implement in an pseudo-ascii graphics set. At the same time I was researching PADC and Ascii Plus graphic sets, and noticed that PADC uses Two Letter combinations for their graphics. I came to the conclusion that I could combine the two ideas for not just demons, but all procedurally generated creatures, and some others besides.
A Symbol signifies what type of procedurally generated creature, while a Number matches to the number the creature would have in extracted raws. Also from PADC I use the idea of a lowercase letter being the creature as a child, and added a smaller letter for babies.
This image is just the concept, not the finished set. Left to right it goes Adult, child, baby, animated, ghost, Law Giver, Prisoner, and Default. The numbers are along the bottom of the image, in order to fit three digits they are turned sideways on the right side of the image.

Credits go to the creators of PADC, Asciiplus, and Dungeon Crawl Stone Soup for the inspiration. And to Lord Nightmare for the letters, and Zarathrusta for the numbers.
The vampire graphics would depend on whether you can give a seperate graphic to a creature based on whether they have a syndrome or not, and would require being added to each civ creatures individually. The reason I have graphics for Law Giver, and Prisoner is that Demons get a seperate tile if they take over a civ. The micellaneous creatures at the bottom are leftovers.
Having seperate graphics for the boogeymen and werebeasts require preparation ahead of time. If you know what your world settings are, then you switch symbols while keeping the correct number after reaching that number.
[MEGABEAST_CAP:75]
[SEMIMEGABEAST_CAP:150]
[TITAN_NUMBER:33]
[DEMON_NUMBER:52]
[NIGHT_TROLL_NUMBER:26]
[BOGEYMAN_NUMBER:26]
[VAMPIRE_NUMBER:26]
[WEREBEAST_NUMBER:26]
the default settings would be to switch to bogeyman at NIGHT_CREATURE_27 and then to werebeasts at NIGHT_CREATURE_53. I just realized I forgot about forgotten beasts!