This site is more for the porn collector or uploader than the user as it is basically an upload site to store individual images and crop them as thumbnails. The homepage is pretty basic and shows three options, flash, file or URL if the file you want is hosted on someone elses website.
Choose one of these and choose a thumbnail size, and after clicking upload you'll be presented with a number of link codes that you can use to link directly to your thumbnail, which has incidentally been cropped!
The maximum file size you can upload is 10mb, and you can register if you want to become a registered user. Files are automatically deleted after 8 months, but that's a pretty long time so this is a useful site for webmasters