Isn't it traditional to show images at a Cinema?

No, everything is "commercials" now.

If by images you mean still images, like photos, not so much any more.

Images of what?

Isn't that the Purpose of a cinema

UPJR is correct, but there are commercials for products, and commercials for TV shows, the latter more like infomercials. These come before the commercials for other movies, aka previews (some folk still call them 'trailers')

Ikr

Yes