I'm a huge fan of the Tux Factory · http://tux.crystalxp.net/en.1.48.html
Sadly not all of those are handy for everything I like. Specifically as they didn't have any Doctor Who
penguins, but I have found over the years there are many tux that're not on that site.
I found this just a little while ago:
Haven't had much luck finding any other of the Doc's rogues gallery though.
Mostly for fun I made · https://twitter.com/TheDoctor_14