I have just released version .80, which I believe addresses the suggestions made in the first comment of this topic.
Specifically:
1. The [mla_gallery] "link" parameter has been enhanced to support linking to any of the registered sized for the attachment; for example, "link=medium" to link to the medium-size file.
2. The new "mla_caption" parameter allows for the inclusion of a wide variety of data fields in the gallery caption. For example, if you code mla_caption="{+date+} : {+description+}", the caption text will contain the upload date, a colon, and the full description of each gallery item. The "mla_rollover_text" and "mla_link_text" parameters have similar capability for other elements of the gallery, and the new Markup Templates are even more powerful.
3. The new attachment-specific substitution parameter "index" allows you to number images in the gallery.
I look forward to more feedback and suggestions for this new release and for future development. Thanks for your continued interest in the plugin.