If you want to use the Lizard for personal use, it's cool.  You can also create fan-art of the Lizard for use in icons, walls, skins etc.  but you can't use the actual lizard image itself in anything you redistribute.

My suggestion?  Put those art skills to the test, draw your own version of the lizzard and use him in your icon set that way 

I always like to see other people's take on our mascot 

Yes....but for those who are clearly scratching collective heads as to why a 'lizard-monkey' would be a 'skinning' site mascot - now they know that 'chameleon' makes so much more sense....