How do you get the desert maps?

I have heard tell of people playing on desert maps and was interested in trying it myself. However the options only has the default map setting. How do I enable desert maps?

I think it’s only available in some of the earlier experimental builds, and I don’t know if those are available for download anymore.

Someone please correct me if I’m wrong.

They aren’t, but i think the availability of creating another mod like it it’s still there.