Texas is well known for its connection to the wild west and its associated imagery. Putting together a mixed media collage is a great way to represent this. Frame the canvas in barbed wire or even create a large outline of Texas in barbed wire. Fill the rest of the canvas with objects in the old west style. Saloon ads, spurs, old newspapers and even boots and hats work well, depending on size constraints. Many of these items can be easily located in antiques malls or vintage stores.
Texas today is a far cry from the rough and tumble old west outpost it used to be. Today it is home to a myriad of urban centers such as Dallas and Houston and it's a national leader in industry and development. Simple, elegant painted outlines of the skylines of the major cities can be a great way to capture this. Paint them on top of each other in different colors or around the edges of a canvas. You could also use the skylines to create a rough outline of the state itself. Nothing is more unique to a state than its skylines and the stories they tell.
One constant through Texas' long history is the ability to churn out some of the nation's most storied musical acts. Willie Nelson and Stevie Ray Vaughn are two prime examples, and Austin still holds claim as the live music capital of the world. If you have the time and space, creating an image of the state out of CDs from Texas musicians is a great way to illustrate the wide range of Texas musicians and the heritage that they draw upon.