This memo about the character of Spock is revealing. It was written as the show headed into its second season and one can see the influence it had on some stories that year. One can also get a sense of the growing difficulties between stars Shatner and Nimoy as they competed for screen time.
Here's a publicity shot of Leonard Nimoy as Spock in the first pilot, "The Cage" and a famous shot of Leonard Nimoy with his 1963 Buick Riviera on the Desilu lot.
Here's a great negative from "The Devil in the Dark" featuring Spock attempting to mind meld with the Horta and two others of Spock with some Treknology.
Here's a contact sheet with images of Mark Lenard as Sarek in "Journey to Babel".
In the lower left is an unused promotional shot of Leonard Nimoy with Jane Wyatt as Amanda in "Journey to Babel".
Here's a famous print featuring Spock by the late science fiction artist Kelly Freas.
This last one is pretty special. This is the only known photo of Gene Roddenberry in a Star Trek costume. This is one of the Romulan uniforms.
The next installment will feature images from "Amok Time".