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(Previous image by Lee Fitzgerald). Here's some early concept art by John Dickenson, who worked on the season 1 Klingon designs; a concept for the bridge by Bartol Rendulic, and a close look at the engine chamber similar to the one in the TOS engine room. 

The reactors (possibly inspired by real fusion reactors) can be seen here in concept art by Mike Minor, who was in the art department headed by Joe Jennings.
1979: The glorious Enterprise refit (designed by Andrew Probert & Jefferies).


Using graphic designer Lee Cole's 'Enterprise Flight Manual', you can assume your duties most effectively. 
Mike Minor's concept for the aborted 1970s TV series Trek, which was adapted for the first movie. Featuring the Captain's Sofa.