GTA SA Texture Art, Cowboy and Alien.

Cowboy

Alien, grey looking alien.

These are all over the Area 69 desert location. Everywhere. Each GTA SA appears to have it's own giant texture mural covered in hidden images. It does genuinely appear to be true that GTA SA has actual map art. These are both apart of a much bigger texture that contains more shapes, but these two stuck out to me the most.

The cowboy being drawn all over the desert could most likely just be a wild west reference, possibly a hint at RDR1.

The alien is pretty self explanatory, it's an alien drawn all over an infamous secret base, as well as a lot of other UFO references in the desert.