Couple of other thoughts, there is the Caddo Lake area of NE Texas off of I20 near Longview, Big Thicket area of SE around Woodville off of I45, then the area closer to Austin around Bastrop, Bastrop state park - know as the Lost Pines, great ferns and lots of pines in an area they aren't suppose to be.
As Lee pointed out the painted churches are a must at some point, as is Goliad. Don't forget the State Capital building, it is really a neat place inside. Please let us see what you find...