A perfect spanking garment for the bedroom might be one of those ridiculous gowns they use in hospitals that have ties in the front but leave the rear bare. Either otk or with the spankee lying on her stomach, be easy and simple to spank.
Shorty nightgowns and pajamas of course are well suited for bedroom spankings(or anywhere-say the lady likes to wander around the house still clad in sleepwear after she get up.
As those who have read some of my stories know, a favorite plot of mine is spanking for wearing too revealing or inappropriate clothes. Rather than discard the garment, have the spankee wear it for spankings in the future, as a reminder of what happens for disobedience. For example, the thong bikini that she flaunted herself in at the beach is now her punishment uniform.