The following flags represent Texas or one of its predecessors. These flags can be used as is or as inspiration.
OTL Flag of Texas. Also Flag of the Republic of Texas (1839–1845/1846)
Republic of Texas Flag (1836–1839; 1839–1879). The Burnet Flag.
Texan Lone Star and Stripes|The Lone Star and Stripes/Ensign of the First Texas Navy/War Ensign; it was the de facto national flag between 1835-1839
Republic of Texas Pilot Flag (1839-1845), and recently proposed for the Governor's flag.
Flag used by Louis de Aury as Military Governor, 1816-1817
Colonel James Long's Flag (1821)
Flag of the Fredonian Rebellion (1826)
The Come and Take It Flag (1835)
The Dodson Tricolor or the Dodson Flag - Designed and sewn by a Mrs. Sarah Dodson during the Revolution (1836)