The small thumbnail images, being displayed at about 80 px by 80 px, are actually 600 px by 600 px images that are over a megabyte in file size each. Displaying that many of them on one page slows things down a lot. Either manually create small and medium size images and put them in the correct folders on your server, or install something like Image Handler to do it automatically for you. Either of these methods will greatly reduce the load on the server and on your browser when displaying pages in your site.

This is a FAQ as well as a fact. ;-)

Rob