Has anyone else noticed that the image of the Discworld itself is taken from the back cover of Santana's third (eponymous) album from 1971 (usually referred to as Santana III)? Take a look at the lower left corner of the picture; it's identical.
And here's a close of of the section (complete with elelphants:
I don't have that particular album, but that looks more like a tortoise than a turtle.
The idea of a flat world on the back of elephants which is in turn carried on the back of a turtle or tortoise is not Terry's originally. It is an image taht has been used for a long time and in several cultures, I believe.
Thaks for pointing that out and welcome to the forum!
The snake could be Midgardsormen, or Jörmungandr as I think it's called on wikipedia, that coils itself around the world.
When the final battle between good and evil comes this worm is supposed to get killed, and mortally wound, the thunder making god Thor.
The worm also got two siblings, one is the god of the underworld called Hel, and the other is a giant wolf called Fenrir.
The snake and the turtles/ellies are (so far as I know) from different cultures/mythology and I haven't seen the two combined anywhere 'reliable' before...
The 2 tail-eating serpents (sometimes called an Ouroboros) as WA says are from Norse mythology (the scandinavian creation myths also feature a giant tree - ash I think).
The turtle/elephant/disc originates in the Orient (where they have elephants of course as well as turtles) and I think it's probably Hindu in origin, although I believe the Japanese myths have turtle gods or demons - no doubt Pooh can help us out there . The article Tony's given us also points at the Chinese and Native Americans having turtle mythology - so a popular allegorical animal-deity worldwide