First, let me congratulate you on the impressive body of rated courses you have on your map. That is quite a bit of work, and well thought out, and done.
Second, the main argument to allow uploading of photos to this site is that it would preserve the integrity of the photo tours. There are many, many tours that now consist of Long blocks of "Image Not Available" placeholders. It is likely these tours will never return.
The other argument that I thought Rich was putting forward was along the lines of creating a new format on this site for creating course commentaries, that would include photos and commentary in a more structured way.
Having gone through over a thousand course threads now, it seems that there was an evolution over the last 8-9 years from the earliest photo threads, to what we see now. The early threads were often no more than 3-4 photos and a "Hey, check this out", to be shared among friends. The popularity and commentary generated seems to have encouraged posters to evolve the form to what we see in the best photo threads today: historical backgrounders, well thought out commentary, quality photos, and strong and compelling dialogue.
However, because the structure used to publish this rich content is a discussion board, these interactive course reviews are also filled with all manner of extemporaneous commentary, jokes, personal comments, travel plans, etc. etc. Now I find this part of the charm of the site, but, I also see the potential, given the energy and enthusiasm put into these efforts, and other models of collaborative content creation, for all this work to be harnessed into a more compelling format.
Wikipedia is the ultimate example of crowd-sourced content creation. In 8-10 years, they have put the Encyclopedia Brittanica out of business. It has its limitations, but, through volunteer contributions by knowledgable contributors, Wikipedia is the World's go-to general purpose reference guide.
The other reason I would give to host pictures here is tied the idea that given the willingness, enthusiasm and knowledge GCA members are already committing to create this treasure trove of insight and reference material on the history of GCA, it is a small leap to imagine a new section of the site that focuses that energy on a more compelling compendium of that history. That new section could, and maybe should, be purpose built to the task, with well defined sections for the history, architects, routings, photos, comments, etc. If that were to come to pass, then for the integrity of that new site, owning the content, text, structure, photos, videos, audio, etc. would be a real plus.
Maybe that wasn't quite what Rich was suggesting, but that's what interpreted.
That said, if you are building a compendium of photo tours of your own, it is easier to keep them separate and just embed them, as needed, within DG image tags.
Dave