Have a look in your phone's relevant Sync Settings as this sounds like your deleting the photos locally off the phone's internal storage capacity but then it's syncing with something like a Google Photo's etc vault or similar which is then somehow returning them for you to see.
If you use a SD CARD then make sure they are being deleted from that too.
Current Phone > Samsung Z Fold³ 5G.
The problem is that it is unrelated to pictures I've ever taken. So I'm not sure of its source, also, its always the same 5 pics. It looks to me like theme images, of people/activities. I was thinking it could be related to an app/theme. But I'm also scared for malicious content on my phone...
I have, and after your message, i've deleted the most recently installed apps. This includes a keyboard editor/personalize function with "themes". I hope this does the trick.
So, after googling a bit, it turned out that the video editor app: VivaVideo, is responsible for adding these images to my gallery every time. I guess it was part of some template? I deleted the app and it the 5 images haven't reappeared. 🙂
Thanks for your suggestions!😁