This effect was generated in Filter Forge, a Photoshop plugin that allows you to create your own filters.
Covers an image with dirt emanating from edges. A muddy texture can also be activated. Highlights on the image can be kept clean.
For non integer aspect ratio landscape images ...
set 'Aspect Edit' to 0.25 + 0.5 * W / H
and for non integer aspect ratio portrait images ...
set 'Aspect Edit' to 0.75 - 0.5 * H / W
Dirt, mud, border