Left-to-right

[Robert Schleif]

Because I read and write from left to right, it would feel more natural to me if the most recently image added to the image browser were to the right of the previously opened images rather than to the left.

[Charles2]

Sometimes I prefer your way, sometimes the opposite. If I could drag a browser column horizontally by its top, File Open window, I'd have both choices available.

[jsachs]

You can move the current top-level image and the images below it left or right with Shift-Left Arrow or Shift Right Arrow.

I agree with left to right as primary, but I think the most recently opened image is generally to most important so it is placed by default at the left.