After looking through most of the category pages for species I have composed a list of the most common species people have categorized their characters as.
Note on accuracy: I didn't count the pages like "Bobs mahjarrat notes" as they're not characters. This might not be accurate due to certain characters being crossbreeds and having all the species they crossbred with in the category's. Plus there might be a slight human error in there as well and some species may be missed out altogether.
In rank order.
1. Humans (571)
2. Mahjarrat (91) (On an unrelated note about 1/3 of the articles under this category weren't characters, they were usually notes, books, clans or user pages)
3. Crossbreeds & Elves ( 73)
4. Vampyre ( 59)
5. Demon (31)
6. Icyene (23)
7. Werewolf (19)
8. Lich ( 12)
9. Dwarves (10)
10. Trolls and Aviansie (7)
11. Orks and Shade (5)
12. Gnome, Goblins, Ents and Dragons (4)
13. Ice Sprites (3)
14. Giants and Fairies (2)
15. Hobgoblins, Dragonkin, Tzhaar and Gorajo (1)
A reminder that this may not be completely accurate.