I didn't put the image in the documentation because I thought I would be taking it out. As it happens, I'm leaving it in.

I think each site can have different settings for its Imagefield, so the importer should conform to whatever settings those are in terms of file type and size. There isn't a hard limit on the size of the files, but you should know that the files are transferred from the source directory to drupal_root/files/ubercart_images on your site.

I'll detail all of this in the documentation today.