Flash Cookies: I imagine that if he can create them, then you can remove them, though I'm doubtful that extensions have full access to Flash internals.

HTML5 Storage: I'm not an expert on the different types of HTML5 storage, though since this is at the browser-level, I imagine the it would be easy for an extension to access them.

Regular Cookies: Obviously extensions have access to these.

Force-Cached PNGs: Not sure what access extensions have, though I imagine that Firefox extensions have a higher likelihood of access than Chrome/Chromium extensions. This is also hard to detect automatically though, unless you want to take the NoScript route and block all force-cached images unless they meet a whitelist.

Web History: Extensions obviously have access to web history, though this is something that would vary from implementation to implementation of evercookie, so it would be fighting an endless battle, like spam email filters. The best fix here would be to close the css history hack hole.