You can browse these forums for several free mutants and chars. Try out our search function.
The old FPSC boards
hold some free characters as well and are relatively easy to get working in Game Guru.
You can find some Doom related monsters here
. However, to get them working in GG you require some scripting and converting experience. There is no tool or other easy import function for external animated characters. Things seldomly work out of the box in game design.
(Just remember that if you use copyright protected characters like Doom monsters you can't sell your game later on.)
This expansion is free,
is GG ready and holds many characters you can modify for your own goals.
Other than that:
We do not allow requests on this board
Read the rules on how to go about this here ..