I understand some images are not loading in Safari. First please review If Safari on Mac doesn't open a webpage or isn't working as expected - Apple Support. Most of those steps are basic and are not likely to resolve your particular problem, but review them for the sake of completeness.
After ruling out all those possibilities read on.
Some people have reported success by enabling or disabling certain "experimental" web features found in Safari's Develop menu. To show the Develop menu, open Safari's Preferences or Settings menu > Advanced and check the box at the bottom. Safari's previously unseen Develop menu will appear. In it, select Experimental Features, scroll to the end and Reset All to Defaults. That will begin troubleshooting at a known condition.
Then, read this post for one possible fix: Images on my website not showing in safari - Apple Community. I had never heard of "Lazy Image Loading" before. It will be found under Experimental Features. Try it both selected and de-selected.
Other factors may be involved, but start there and let me know what you determine.