Gosh, there is so much to see. Knowing your interests would help.
Big Bend State Park is awesome. There is also the renowned McDonald observatory at Fort Davis very near there. Further east is San Antonio. A very beautiful city, 7th largest, which is a major tourist attraction. With sites such as the Alamo (and four other sister missions, on Mission Road), the River Walk, the Hemisphere Tower (built in 68 for the North American world's fair). San Antonio has many other attractions such as the #2 rated zoo in the United States, behind San Diego, if my information is still correct. Great museums and a very nice Chinese Tea Garden.
Texas also has pristine waterways, which are plentiful. We also have a beautiful coastline and coastal areas inlands.
Texas is also ethnically diverse with many communities rich with flavor from the originating countries. We have French, German, Irish, gosh, with all the rest I would need help being accurate. We of course do also have a heavy Mexican heritage, having won our independence from Mexico'
Texas is truly a destination state. My info will get you through the southern part. Further north you could see the Palo Duro Canyons which you could then go through the Amarillo area then on to Oklahoma and the mid west.
Again, knowing your interests, time frame, and route would better help us to help you.
Enjoy your tour.
Dont come to Waco. Theres nothing here.. i hate it..i went to SanDeigo and LA last year and now want to live there.. the oceans are amazing unlike Corpus. If anything i would say go to austin..party city