A very early build of my new WB Skin Randomiser is available at http://pjpowell.dyndns.org/Downloads/SkinRandomizer.exe
This displays all your skins in a long list (main skins and subskins) and allows you to group and save the names to a file. Then you can load groups as and when you like and set the timer to change randomly between them.
Bear in mind I only started writing this yesterday but any opinions/requests for features would be most welcome. This does require that Skinstudio is installed. If it doesn't work for you please let me know so I can try to resolve the problem if it's something my end.