None of these :).
Install photo-book, upload pictures there. Write a browse functionality that let's you copy an <include src="/packages/photo-album/www/random-photo" photo_id="8107"> to the clipboard (or into the edit this page function). If you want to have multiple random photos, give the album or package_id instead.
If interested, check out http://www.sussdorff.de/about (stock ETP) or http://www.thecodemill.biz/ (with pictures enabled in logger).
