Discworld Noir Easter Egg - Discworld II Revisited

Whilst inside the Pseudopolis Yard have a close look at the paintings on the back wall upstairs.

The one on the right is clearly the same Unseen University artwork from Discworld II.

The left painting is slightly harder to make out, but it appears to be the forest from Discworld II where the portal to the Elfen Queen's realm was hidden.