May I suggest you look into grype[0], or some other similar tool? It can be used to scan images for vulnerabilities. You'll probably find a bunch of vulnerabilities that aren't likely to actually affect you, but still, at least you'll know they're in the images you're running. And maybe you'll start using things like docker-slim[1] on your own images to get rid of those vulnerabilities you do find.
Yes! I frequently review any containers from the cloud I run. Load on isolated VM, start, cursory inspection at least. Then with images I'm happy with we keep them internally, until we need the upgrade.