You'd be surprised. One thing that impresses me about Dallas is its "bigness"; it seems like a large-scale place because it has large buildings like other urban centers, but is quite sprawling and not so compressed.
One of my favorite "themes" in the Dallas area (my parents live in Lewisville, an exurb that is north of the city along I-35E, a half hour south of Denton TX) is the effect of the hand of man upon nature; the explosive growth of exurban sprawl; the stark beauty of the terrain (best seen, I think, as you go north beyond the city, past the inner-ring suburbs and onward towards Oklahoma.
You really will need a car to make getting around easier. But even if you only have time to walk about downtown, there should be plenty to catch your eye.
Aside from shooting, if you're up for a museum, and find yourself with a few hours to kill, the Amon Carter Museum in Ft Worth is a must-see. Excellent collection of photography. Not too tough to get there if you have a car.