http://www.gamesas.com/bgsforums/index.php?showtopic=917737&st=0&start=0
Decay slowly
This was mentioned a few times in the first Lichdom topic I created about decaying slowly so you're not all skeleton or zombie looking all at once. The process would take a while you would not look undead immediately but after a period of time.
Path to Lichdom
In the previous post it was pretty unanimous that Lichdom should be a very long process that is not easily accomplished. This isn't vampirism where your bit three days later you're a vampire. Lichdom is an entirely different beast, it should take several hours to become a Lich whether or not you taking your time or doing it as fast as possible. There should also be multiple ways of becoming a Lich I highly doubt that all Liches prayed for the knowledge to become a Lich from the Great Sovereign. Or that the process was the same for everyone.
Perks of being a Lich
Well the obvious should be serious magic resistance, reflection and absorption. Some other benefits should include joining the undead faction so normal undead won't attack you unless provoked. Lich only quests that you must be Lich to be able to do. Command undead power that makes undead do your bidding. There were quite a few other ideas that were kicked around as well. The casting costs on summon undead spells would be reduced, some undead would just be a lesser power that allows you to summon undead freely or cost next nothing. You might gain followers/ worshippers that do your bidding, possibility of creating your own faction.
Downside of being a Lich
You won't be able to do certain quests. NPCs react negatively to you with low level peasants running away in terror or frozen in horror by your presence guards and high level NPCs would be hostile towards you maybe even try to kill you on sight. Social interaction is almost impossible without Illusion spells and even then it should be very difficult. Priests and servants of certain religions (Arkay for example) might try hunting you down and destroying you. You won't be able to use altars or other services of certain religions you may not be able to enter certain churches because you're undead (sort of like how the Daedra can't enter the church in Oblivion's MQ). Overall Lichdom is a very lonely existence.