Sometimes users get the issue that their images are not visible on the site after activating SSL, but the images are loaded with SSL links, and load fine when loaded directly. So this is not a mixed content error.
When you look in the Chrome console (right mouse click, inspect element, console), you see a lot of red error message, all stating that the image has a 403 forbidden error.
In most cases when this happens, the hot link protection is enabled. By adding the https domain to the settings in the server this issue was solved. If you can’t change this yourself, please contact your hoster to fix it.