What follows is a collection of sources that in some way describe the Karankawas’ tattoos:
[1833-1834] John Charles Beales’s Rio Grande Colony: Letters by Eduard Ludecus, a German Colonist, to Friends in Germany in 1833–1834, Recounting His Journey, Trials, and Observations in Early Texas
Author: Eduard Ludecus
Written In: 1833-1834
Description: Eduard Ludecus and other settlers rest and resupply in La Bahía (Goliad) on their way to settle along the Rio Grande. In the ramshackle city of La Bahia, and in the missions in close proximity, they encounter Karankawas.
(1) Ludecus inaccurately states that “when Colonel Austin’s grant was settled, they [Karankawas] invaded there [Austin’s lands] and killed anyone they found.” This is backward, but it shows that Anglo-Americans, Mexicans, and Tejanos believed this falsity. Ludecus received this information from Holley Austin’s account of Texas (Austin Holley, 95-97). In essence, Ludecus is already biased when he first encounters the Karankawas. He sees these Indians as always looking to steal and murder.
(2) Ludecus then goes on to state that Stephen F. Austin “succeeded in exterminating half the tribe.” A large group of Karankawas fled to La Bahía, where Mexican officials murdered half of the survivors.  As already mentioned, all this information has come from Mary Austin Holley’s Texas. This information is not unique. All the following information that Ludecus provides is unique.
(3) Ludecus refers to Karankawas as “well over six feet tall” and gives a detailed description of their tattoos, piercings, weapons, and dress. [pages 79-86]
(4) Ludecus provides a great deal of information about Chief Prudentia. He also describes that Dr. Beale asks Prudencia whether he and other Karankawas would like to join the settlement. [78-83]
(5) States that Comanches and Karankawas are “mortal enemies” at this time. 
Access: Eduard Ludecus. John Charles Beales’s Rio Grande Colony: Letters by Eduard Ludecus, a German Colonist, to Friends in Germany in 1833–1834, Recounting His Journey, Trials, and Observations in Early Texas, ed. and trans. Louis E. Brister (Austin: Texas State Historical Association, 2008).
Further Reading: For a well-written overview of the Beales colony, see Kyle B. Carpenter, “A Failed Venture in the Nueces Strip: The Mismanagement of the Beales RioGrande Colony, 1832-1836” The Southwestern Historical Quarterly,(Forthcoming Spring 2020); For another source on Cheif Prudentia see Kelly Himmel, The Conquest of the Karankawa and the Tonkawas, 1821-1859 (College Station: Texas A&M University Press, 1999), 52-53.