I finally got Photon to correctly upload my pictures, only to discover that

(a) it wants to do a separate post per picture, and
(b) the default MT stylesheet wants to clip my pictures horizontally, and I'm too stupid about stylesheets to get it to work right at the moment.

So pictures may return later when I feel like fighting with MT some more. So this is the one thing Radio does better out of the box so far. Wheee.