Hi, apparently skin tone 80 and skin tone 175, both used by yuan-ti npcs everywhere and race appropriate tones are actually not selectable at character creation. The peddler in Saltspar, for instance, uses 175, and most of the male yuan-ti mobs in the server used skin tone 80 before the area full of yuan-ti was removed from Sibiyad. On top of that, both in 3.5e and on the server these same NPCs often used the lizard tail available on the pgcc. Yuan-ti purebloods are well known to sometimes have tails in most of the 3.5e art I've looked at, particularly the books all about them. It'd be fun to be able to create more monstruous yuan-ti.
I posted a gallery of them below.
And here's the sourcebook with a lot of this supported: