I love the smf forum it looks so much better than the phpbb2 forums ive used in the past, the only thing that i cant seem to do is add cutom ranks or remove the ranks for the admins and mods? :-\
You can add custom titles in the profile, which display in addition to the post rank. Or, you can create custom ranks by going to Admin -> Membergroups -> Add Group.
You can remove the postgroup ranks for Mods and Admins by going to Admin -> Current Theme. Scroll down to the bottom, and you should see the option "Hide post group titles for grouped members?"