The titles for the 3P forum are as follows:

Start: Imp
15 posts: Grindylow
30 posts: Diricawl
50 posts: Ramora
75 posts: Doxy
100 posts: Fairy
150 posts: Pixie
200 posts: Puffskein
300 posts: Kneazle
450 posts: Ashwinder
600 posts: Hippogriff
800 posts: Runespoor
1000 posts: Centaur
1500 posts and up: Demiguise
Of course these have nothing to do with their classifications, just my personal preferences.

Staff get their own titles, available upon request, for any magical creature not listed above.
Examples of staff titles:
Sphinx
Lethifold
Griffin
Unicorn