Are these images you are trying to view on a web site or through Photos? If it is on a web site, do you have content blocker on?
Do you have JavaScript enabled in your browsers?
Any plug ins installed ? (flash player)
Yes, safari and computer have been restarted.Now you should quit Safari, then start it up. Those images should show up.
Is your System Preferences/Displays pref pane set for default resolution (and NOT a scaled setting)?
Can you log in to another account, and check if the images are still the same?
If you don't have another user account, this would be a good opportunity to make one, just for troubleshooting this issue...
If none of that helps, you should run your built-in diagnostics - https://support.apple.com/en-us/HT202731
Come back with any reference codes that might be generated by that test.
When you ran the diagnostics test - that likely scared your poor laptop, and made it behave.