We would like to use it for archiving of historical photos and then presenting them back to the public.

However, if there was a way for user to create multiple custom fields or groups..

IE we need:

Donated by:
Date of Photo:
Location of Photo:
Category of Photo (Multiple) (School, City, Farm, ect..it may have multiple categories)
Sharable:
ect..

And be able to search on these fields.

Everyone would have diff needs for diff fields, and some fields may be of diff types, however the database would have not issues supporting this depending on how you design it..

You rock by the way.