It turns out that clown spankings have been a thing for awhile:
According to Valdor at Spank Statement, this photo is by photographer Kyer Wiltshire and it was used to advertise the 2009 Clown Burlesque Extravaganza in California.
"...the girls are prepared in the reformatory’s punishment room, naked, lying on their backs on special benches, bound with their legs spread above their heads, shamefully showing the two holes usually hidden..."