In its default settings, uMatrix content blocker allows CSS and images (JPG, PNG, etc) from all sources, unless denied by a site-specific block list. It also allows 1st party cookies, scripts, and multimedia.
How much can a 3rd party learn about a site visitor through only CSS and images? Assume an up-to-date standards-compliant browser that lies about :visited status.
Obviously they receive HTTP headers (IP address, userAgent, etc) and can determine some browser features through media queries. They can tell if you choose to print, and possibly how long you keep the page loaded.
I think :hover pseudo-classes could (partially) track mouse movement.
What else can be done? Are the capabilities sufficient to provide unique fingerprinting across multiple sites, effectively a super-cookie?