How to delete Images on Android 8.1.0?
These are the caches Images which Android stores it in itself. To delete these Images, go to your File browser and allow the File browser to show Hidden Files and then Go to 

Phone Storage > DCIM > .thumbnails

There are image more than 100 image and some waste files stored under this folder. Delete whole folder. Doing this can help you in some Manner to get out of dwindling storage.