This program (JaFO's Bot-Editor v2.0) (ut'99 version) can help you to change the user.ini file
Code:
http://jafo.mienadres.nl/
Also add the skins to your server ini as a serverpackage, and make sure the skins are complete (heads, teamcolours, etc.)
@ Filthy_Few: I guess the adding the skins as a serverpackage will do the trick for you