Tzvi informed me today that Firefox 3 supported ICC v2 and v4. For someone who dabbles in photography, this is good news - photos should look the same across browsers and platforms. When checking the color.org site on ICC and browser support, however, I found that the images still did not display correctly. It turns out that ICC is off by default. To turn ICC support on, go to about:config, set gfx.color_management.enabled to true, and restart Firefox.
There, now photos will look as good in Firefox as they have in Safari/OmniWeb.