Here are a few suggestions along I-10 as you head west:
Caverns of Sonora outside Sonora, TX.
Fort Lancaster Sate Historic Park and the scenic drive into Sheffield along TX-290.
From Fort Stockton, TX, I'd head north on US-285 to see:
Carlsbad Caverns and
Roswell, NM, as themed a town as you're going to find on this route.
AZBuck