i have found a great free website of 3d ressources, there is some 3d models of robots, who can probably be convert into infantery for ra2/tsun
Note that some need several textures. The file extension is for 3dmax

WARHAMMER 40,000:

marine: http://members.ozemail.com.au/%7Edproc/marine.htm


ALIEN
cray APC, i love it ! http://members.ozemail.com.au/%7Edproc/apc.htm

WHAOU the dropship of alien (i love it) http://members.ozemail.com.au/%7Edproc/dropship.htm

USS Solaco of alien http://members.ozemail.com.au/%7Edproc/sulaco.htm

The robot Dock of alien http://members.ozemail.com.au/%7Edproc/loader.htm, just need to be armed



OTHER (starship troopers, martian invasion...):

a martian ship http://members.ozemail.com.au/%7Edproc/martian2.htm

A weapon rack, http://members.ozemail.com.au/%7Edproc/weapon.htm who can be modify to make a good building, or something else

A huge carrier http://members.ozemail.com.au/%7Edproc/carrier.htm

a battlecraft http://members.ozemail.com.au/%7Edproc/tc.htm

I hope that will help you