Does it have the feature where the file can be truncated to any size to form its own thumbnail? That would be an incredibly useful feature in so many applications.
Some wavelet formats (SPIHT and EZW e.g) have the property that truncating the lossless version at 10% of the size gives you the 10:1 lossy rendering of that picture. That property holds not just for 10% but for any fraction of the file.
It's not quite the same thing, but a very highly compressed high-res picture would probably look okay in thumbnail format.
