Yes it is possible to create completely new figures for iClone. The current software requirements for this are 3DS Max. You will also need the Max plugin and the figure templates which includes the bone system etc. Both of these are free to download once you register your software and become a member of the developer program.
Take a look at the Developer Center for more information.
http://developer.reallusion.com/default.aspx
Peter EdwardsForum Moderator
iClone Daily Blog