Okay, just for fun, let's look at the SRD and start listing some fun critters to include in a "warm desert".
Baselisk is a "Warm Desert" creature.
Blue Dragon is a "Temperate Desert" creature. We might be able to stretch that one.
Brass Dragon is definitely a warm desert creature.
Janni are classic warm desert creatures, and may well substitute for Bugbears.
Lamia are "temperate desert" beasts.
So are Lamasu.
And who can forget our old friends the Sphinx family?
And while Hyena are no threat to the party, they'll play hell with the horses. I can see the party reacting to them with disdain, knowing that they can't hit PC armor classes, then realizing that their horses aren't as well armored.
Then we get to things like Monstrous Scorpion. The Colossal one has +15 to hit, and his poison is a DC23 Fort save or lose a D8 of Con. Though he's only a CR 10, he'd be a threat. Add in a few smaller ones, say the Huge ones, and you have an encounter.
Hmm. Ac 24 and 150 hit points will fall to the party fighter in two rounds. I'd better throw a couple of them.
And that's just from the SRD, which harly goes beyond MM I. Other MMs and the Sandstorm book will get me even more toys.
Yes, I think this will do nicely.
I think we have an adventure.
Thoughts? Comments? Suggestions?