Hello
I find this very useful, and by far the quickest tool for this as for now!
I have two feature requests.
* I'd like a http-get option for screen port size. Most sites I use thmbalizr on has a static width of about 800px, and that makes the preview mostly background. A "...&sps=800" where you can choose a screen port width between 500 and current (1200?).
* I would also like for a boolean option to put the thmbalizr logo at the top of the image instead of the bottom (now that is has to be there)
I have made a small greasemonkey script using your sevice to show thumbnails of my del.icio.us bookmarks! It will soon be published here.