Oh nice, themebeacon seems much more comprehensive than themefinder.
For the speed issue; I was playing around with an idea of preloading the iframe previews to speedup loading; it worked but the browser would crash due to high CPU/memory usage eventually. Maybe you'll have better luck?
For the speed issue; I was playing around with an idea of preloading the iframe previews to speedup loading; it worked but the browser would crash due to high CPU/memory usage eventually. Maybe you'll have better luck?