With a blank gif you'll only get what the browser sends. You could set a cookie and track that (to see who else visits sites using your analytics tool), but you

With a blank gif you'll only get what the browser sends. You could set a cookie and track that (to see who else visits sites using your analytics tool), but you're unlikely to be able to pull data about flash configuration, javascript engines, browser resolution and certainly wouldn't be able to build heat maps.