Hmm... I would think the brown colored layer in saturation mode wouldn't work in all cases. It really depends on the picture you're working with. I haven't figured out a formula for determining what color works or doesn't work, but playing around with different colors and trying each blend mode (and opacity) helps!

I have a couple of LiveJournal icon tutorials saved that I'll point you to:

http://community.livejournal.com/__belfrycons/4439.html (this one was done in Paint Shop Pro but should also translate to Photoshop, GIMP, etc.)

http://community.livejournal.com/color_freakshow/1692.html

They really break down each step and help set a foundation for giving photos that "look." But again it really depends on the photo you have, as you might not need to do all the steps for certain photos.