Caching of the Thumbnails

[lumpen5]

The Thumbnail service i use (artviper.net) has been down a few times in the past week.

Is there a way to cache the current thumbnails (when the site is up) so that when the site goes down I can still have thumbs showing? Or would it be too hard too integrate?

Also, (I'm sure this has been discussed to death) Is there any thumbnail service that people think is the best (free) service?