Texas is quite reasonable on custom license plates, and it offers a very large number of plate designs. The plate design costs $25 extra and the custom letters/numbers cost $40 extra. This is on top of the $60 annual fee for the registration. All Texas plates are automatically renewed every three or four years at no extra cost, to keep the reflective surface and the holograms (in the Scotchlite) in good condition.
I have a God Bless Texas plate with a Lone Star Flag and custom lettering MTNST (empty nest) on the Suburban which cost $125, and my wife has a Bluebonnet (state flower) plate on her car, no special lettering, at $85 yearly.
You can get all major texas university plates, and also some out of state universities. I have seen a couple of University of Oklahoma Texas plates. That's similar to the one pictured earlier with the New York Yankees frame in Massachusetts. Brave souls, but Texans are generally friendly about things like this, especially during any year following a UT victory over OU in football.
Railroad themed plates? Texas is not the place where they are most common. Maybe I should change mine to ATSF YALL or TX CHIEF or MR P&SF or PLAINS DIV.