Here’s a third test, with links to 6 different flickr photos, which all happen to be in the same set. It includes 4 landscape and 2 portrait photos, to see how those work. The result is that they all get shown in sequence, you don’t get the posterous “album” that you get if you attach multiple photo files (rather than links) to a page. By default the portrait photos were left justified, I edited the post afterwards to make them center justified. The Landscape ones filled the whole width anyway so justification didn’t matter.