While Ken is correct about there being not much scenery between here and McAllen, the drive along TX 35 to Corpus is definitely more scenic that going down US 59, because you run along and around some of the bays. Depending on what you like to photograph, you can find some interesting things to shoot in Palacios, Port Lavaca, and on down around the Coastal Bend. The Fulton Mansion is pretty much a "must see," in my opinion
http://www.visitfultonmansion.com/index.aspx?page=10. The Aransas National Wildlife Refuge is on the Houston side of Corpus, and the North Padre part of the Padre Island National Seashore is on the south side.
From Corpus, you can go down either US 77 to Harlingen and back up US 83 to McAllen, or you can continue past Robstown (too bad Joe Cotton's BBQ joint burned down earlier this year) to US 281 at Alice, and drop straight down to McAllen, or you can go down one way and come back the other. You'll probably be in more of a hurry to get back home, so you can take US 77 north out of Robstown to Victoria, and then come back in on US 59.
Either way, the cattle and rattlesnakes pretty much outnumber the people between Corpus and the Valley. Each of the few small towns along the way has old buildings and such to photograph. There is a tour of the King Ranch out of Kingsville that I thought was rather interesting
http://www.king-ranch.com/guided_tours.html. I haven't been down that way in years, but I seem to remember the last time I went through Victoria, I saw a section of town that had a bunch of old houses. Been meaning to get down there to check it out, but I haven't made it yet. Oh, and if you do come back up US 59, you'll certainly want to get off the highway and drive through Wharton, so that you can get some classy photos of the Teepee Motel
http://www.teepeemotel.net/.
There was an article in
Texas Highways late last year or earlier this year that had some things to see and do down in the Valley itself. If I can find it, I'll link to it.