Do not ask a photo editor to run pictures of people who are not in the show, photos of an aging danceuse that were taken in her youth, or photos of settings that are not in the production. When the production is a premiere, you have an advantage in publicity because an opening has implicitly more news value. But as you have not yet mounted the show, you are in the peculiar position of wanting to provide photos of a production that has not yet happened. Designing these pre-production photos casts the producer and publicist into the role of an art director. This a truly creative, enjoyable process that should be relished, not dreaded.
People perform for people.
You are popularizing people. So, show the faces. The costume designer has always been part of the team in pre-publicity photos for Jean Cocteau Repertory. Use costumes and props. The cooperation of your set designer and costumer is often required in creating photos that are distinctive to your production and also pleasing and interesting to look at.