I submitted a URL to Digg but didn get an option to choose a thumbnail. Why not?
We try to ensure that you can choose a thumbnail for all sites that are submitted to Digg. We allow you to choose a thumbnail for any image provided it is at least 80 pixels high or wide and in the .gif, .jpg, or .pct format. If you are a site owner, you can follow our sending us a bug report using our handy form. We appreciate your input in making sure our site is the best it can be.