Let's get with the spanking stuff already.

Best prompt format from my testing.

[photograph | digital art | drawing] of spanking corporal punishment. 

a [DESCRIBE PERSON] is lying on a [DESCRIBE PERSON]'s lap.

Also the keywords:

skirt lifted

pants pulled down

revealing [ass | underwear | panties]

For example:

photograph of spanking corporal punishment. 

A woman is lying on a man's lap. 

The woman has blonde hair.  Her skirt is pulled up revealing thong panties.

The man has dark hair.  He is wearing a shirt and blue jeans.

They are on a train.