I too have been confused about the database category for documentation. At first I wondered if it's use was for text only but then I noticed some really nice photographs of botanical drawings in that category. The word documentation had me looking up it's definition and I guess there can be two different interpretations, one for written text and one for photography.
Written Documentation:
Material that classifies and annotates text, photos, etc.
Material providing evidence to substantiate data in a book, article, etc.
Material used to describe or explain attributes of an object.
Material recording facts relating to a subject
Photographic Documentation:
A narrative or story told through photographs
A factual record or report (sometimes complimented with text)
A photo used to chronicle events
A photograph documenting the appearance and condition
Whenever I enlarge a database photo, I don't really pay any attention to which category it's in but I think it's really helpful to see photos that show the details of a plant grown in different lighting conditions.
I'm not sure if there's a way to indicate in the database exactly what should be uploaded to the documentation category but it might be helpful to members so they don't erroneously upload photos to that particular category and it would also make less work for administrators who have to move images to a different location.