I'm pretty sure its ok on Texoma. I've seen people camp on the islands and we've beached our boat on them and slept in it overnight. There are some concrete picnic tables on one of them. I'm not sure if there is a closer access but Highport Marina is a close paddle to them.
I've known guys that have camped on Ray Roberts, Lewisville, and Grapevine islands but I not sure if it's allowed. As mentioned Broken Bow. Also a really nice island lake and less than 4 hours is Lake Ouachita.