Finally, I have added a new, empty layer, set to multiply mode, filled with "multiply-neutral color (white)".
I have selected the foreground color on my color picker from the darker warm parts of the image.
And I set my gradient tool to Linear, foreground-to-transparent, and draw a gradient in from the left, another from the top, and a third from the bottom.
I fade the gradient layer to suit, and I am done, except for sharpening and resizing.
I resized the original to 1600 pixels, flattened the image, duped the base layer and used "sharpen" on it, duped THAT and sharpened again, duped THAT and sharpened a third time, then resized to 800 pixels.
This was too sharp, so I tossed the top layer. It was still too sharp, so I faded the second layer to 25%. That worked, and i saved for web.
While photo tools is downloading :), just to say what a great way to share your work, thank you!
Clicking back and forth on this tab and the final product, I've just realized how subtle is the sharpening.