The desert has only showed up thrice before.
The first time was in comic #44, when Cyril was dreaming and/or has a flashback. The dream included (in order):
-Cyril finds himself in a desert -his parents come, saying they are leaving him there, and have adopted a zombie instead. -As the parents leave, one of them says that there are desert pythons (not in-game) and leaves.
The second time was the Mother's Day comic, in the second panel.
And then it shows up again on recent comics, where Maxx and Cyril are in the middle of the desert.