We add new fonts to the Typekit library all the time. Fonts are carefully evaluated before being added to the library, and we often work closely with our foundry partners to optimize fonts for the web before releasing them. We have a preference for great text faces, but will also accept outstanding display faces. We do not typically accept pixel fonts, grunge fonts, ornaments, or dingbats.
You may request a particular font by sending a note to firstname.lastname@example.org.