Example:

<a type="image/jpeg" title="JPEG - 26 ko" href="/sites/default/files/example.jpg"><img width="150" height="113" alt="JPEG - 26 ko" src="local/cache-vignettes/L150xH113/example-e37e5.jpg"></a>

It seems a filter is needed here too.

A good solution could be to get rid of upload.module and jump to http://drupal.org/project/galleryformatter