I'm going to have to look at my copy when I get home now. And check if the Koom Valley painting from thud is a reference to anything that actually existed....

The Night Watch is parodied on the British cover of Terry Pratchett's 2002 book by the same name. The cover illustrator, Paul Kidby, pays tribute to his predecessor Josh Kirby[22][23][24] by placing him in the picture, in the position where Rembrandt is said to have painted himself. A copy of the original painting appears on the back cover of the book.