It appears that the boys have been spanked. Note the hand positions and redness. The girls are nearly unclothed, yet are wearing shoes. They must have been wearing dresses that were removed, else the shoes would have to be removed and then replaced. Not impossible, but less probable.
I think the tile patterns are just simple backgrounds to prevent any blank areas in the pictures. Easy to draw. Easy to add. Performs a purpose. Occam's razor.
I would like to see the other end of the "pool." That would likely shed light on this pool-looking area's function.