I don't see a problem, its Josh Kirby artwork on a Discworld forum with no intention to promote or sell anything.
Josh also did covers for Tom Holt a UK humorous fantasy author and a few other in the same vein.
Re Robert the pyramid and the various characters depicted are from the Bretford Triangle the first book of
four in the trilogy.
![Wink ;) ;)](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
(IMO the best of all in that particular series well the first three)