I downloaded Exifer's successor
Geosetter seeing as it's being updated and it seems to work similar to how tsaint described exifer above (with added options re GPS data which can be easily ignored).
With GeoSetter you can tag an image with
Category, Supplemental Categories &
KeywordsI've never tagged images before so I'm wondering, could I also use the keywords to describe the quality of the image e.g.
People | Family/Occasion/etc. | Person's Name/[RATING]
could even give it a rating e.g. 1 to 5.
Idea being I can later filter by image quality as well as content.
Does that sound feasible ? 
(I'm putting the cart ahead of the horse here a bit - I havent even installed software yet that can read tags

maybe I should go do that now, I have an older copy of AcDsee that I think will do as much as I need)