One need not be an artist to generate such a picture. One simply has to have the necessary software. Then one uploads the thousands of individual little images (here: of the thousands of fans) and the single main image (here: of Leonard Nimoy giving the Vulcan salute taken from the episode "Amok Time"*), and the program automatically generates the composite image.
Regards,
*Yes, I admit that I'm a Trekkie - look for me in the palm of Spock's right hand.
I LOVE IT!!!!!!!!!!!!!! Thrilled to meet a palm!!!!!!!!!
Thrilled to learn this. Had no idea. Have seen them before but have always been awe-struck. Well, still am, even with software help.