Returning to some issues touched on in my original post, a distinction that I did not initially appreciate, but no do, is that between the criteria for creating an article on Wikipedia, and uploading an image to Wikimedia Commons (where Wikipedia is just one of their potential downstream uses). In the present context (e.g. folk music artists), Wikipedia has a "notability" criterion which means that the person/artist/act must have been recognised by third parties as being "notable" in some way, such as magazine coverage, music release on a recognised label, etc. etc.
For Wikimedia Commons, however, the criterion is simply "useful for educational purposes" which is much more in the eye of the uploader. This is why I think it is valuable to use this site to document a number of the more "minor" and/or transient folk related persons and events on the basis that in future years, *someone* may find it of cultural value - while still excluding the "purely personal interest" (parties, friends, self, breakfast) that clutter up so many other photo sharing sites of a social nature.
In other words, Wikimedia Commons sits somewhere in the middle of a continuum between "significant content" and complete rubbish, and that suits me and my present purposes just fine. It also fulfils several other important criteria in my mind, including (hopefully) persistence (since there are presently 50 million images there and rising, someone will care about maintaining the archive into the future) and discoverability (it is one of the big players in the image hosting world, plus its search function works well), as well as being a not-for-profit / foundation backed operation, unlike e.g. Facebook, Google photos, Flickr and the like.
Just a few random musings from someone glad to be able to shift the burden of ongoing maintenance of my files to someone else, while retaining the facility to edit captions in real time as needed, discuss images further via a "discussion" function, etc. I have no doubt there are other ways to do this too but it seems a good solution for me, both in theory and from my experience to date.
Cheers - Tony