The Images tab is a work list rather than a gallery. It counts the images in each part of your group and shows how many are still missing their alt text or their credit.
Images in the group settings opens on a table with one row per location - Film poster, Photo, Content block, Event teaser, whatever the group actually has - and columns for how many images are there, how many lack alt text and how many lack an attribution. A Total row closes the table. Three buttons sit above it: Images, Attributions and ALT tags. The two work buttons turn yellow while their count is above zero.
Write the alt text
Open ALT tags and describe each image in a sentence, in every language the site uses. A language with no text of its own falls back to the default language.
Credit what needs crediting
Open Attributions and type the credit next to any image taken from the internet - "Photo by Jane Doe on Unsplash, CC-BY 4.0" is the shape. It appears on your public Image credits page, linked from the footer.
Mark your own photos
Set MyImage to Yes for pictures you own or that are public domain. That clears them off the pending list without inventing a credit.
Alt text is not optional in the same way a credit is
A missing credit on a Creative Commons image is a licence problem. A missing alt text is a person using a screen reader being told nothing at all, on every page that image appears on. The platform tracks both, and the notification bell will remind you about the alt text.