Just some links to old and new Tékumel stuff on the 'Net:
Alfrik posts about his Atlanteans (we know them as Mu'ugalavyani) on his blog and at the Lead Adventure forum - a nice collection including non-humans!
Katherine J. Grantham's work has graced many official Tékumel publications - some of her work is posted at Elfwood.
Mark Allen is another illustrator working on Tékumel projects - lots of good stuff on his blog, Marjasall Productions.
And, if you are not reading Howard's The Tékumel Project blog and Chirine's chirine's workbench blog, you are missing out!
(This is by no means everything out on the web for Tékumel - just a few tidbits I have looked at recently)