On the edit form when you are creating a new page, you are given an option of page types that can be used. The string presented to the user here is not particularly friendly: e.g., mdwn, txtl... it would be nice if the drop-down contents were "Markdown", "Textile", etc. (the values in the option tags can remain the same).
I've written a first-take set of patches for this. They are in git://github.com/jmtd/ikiwiki.git in the branch "friendly_markup_names".