We have had open discussions about these questions here on the forum before. I'm no lawyer, and will refrain from any comment on what can or can't be done, in terms of posting url links (either direct or embedded) to web pictures. I welcome the discussion (openly, in a thread, if you so desire), but am simply not armed with enough info on my end to offer any definitive decree.
I do know (as reported here by others) that some sites such as railpictures.net are quite protective over their images, and offer usage restrictions quite clearly on their website.
