When I worked in the late 70s for a PBS station, we used to be supplied 35mm slides with show logos, stills, etc. for use in local promos as well as scripts to be read in conjunction with the slides. I'm pretty sure the commercial stations had the same type of publicity stuff. I've seen art cards for game shows on ebay. I wonder if there are any 35mm slides for game shows in existance.

We used 35mm projectors on P+ but they were on stage as part of the set.

Art cards, commonly known as "flips", were standard.

I have over one hundred 35mm game show slides in my collection. Most press kits come with at least one 35mm slide. At least two different press kits in my collection came with between 15 and 20 slides apiece. As The Donald said, check eBay.

I didn't read your original post carefully enough. Art cards were used for in-studio prize plugs. Network affiliates would get a 35mm slide with the show logo, network logo and the emcee in some sort of dorky pose to be used as "standby" slides (in case of technical difficulties).