Liches look fully like skeletons. They can be said to be even more stereotypically undead than vampires and therianthropes. They literally sold their living bodies for eternal life and more power, being completely free of the chains a mortal body has. They are servants of darkness forever, there is no option to turn back anymore. Besides, who would give the option of a redemption to a talking skeleton anyway?
But why would anyone turn into an ugly lich if he/she could turn into a beautiful vampire? It can have multiple reasons. Maybe he/she doesn't meet the demands to become a vampire, so they do not do it that way. Or maybe the dark wizard works alone only and doesn't need friends, nor master. After all, vampires are social creatures who prefer to operate in clans rather than in working solo, Only the strongest dark wizards and necromancers can turn into a lich.
The ritual under one becomes a lich is a dangerous one, and is usually lethal to anyone who isn’t sufficiently prepared to do the deed.
Enabled aligment: anything Evil