In Saints Row: The Third (aka Saints Row 3) for the PC, PS3, and Xbox 360, there are several outfits that you can unlock for your gang members to wear in the gang customization screen.
Here are the gang outfits you can unlock, and what you need to do to unlock them.
Cops/SWAT – Complete all Snatch activities for Kinzie
Deckers – Complete Mission 37
Ho’s – Complete all Snatch activities for Zimos
Luchadores – Complete Mission 43
Mascots – Complete all of Professor Genki’s S.E.R.C. activities
Morningstar – Complete Mission 29
National Guard – Complete all Tank Mayhem activities
Space Saints – Complete Mission 47
Strippers – Complete all Escort activities for Zimos
Wrestlers – Complete all Tiger Escort activities