Someone asked about a gel effect
It occurred to me that if you copied the layer
containing an image, turned the copy's saturation all
the way down and the lightness up using the hue
saturation tool, made sure the copy was above the
original layer then turned the opacity of the copy
layer down it might look like a gel effect and it did!
You could use a layer mask to restrict the effect to
only some areas or maybe paint in the splashes of white
or gray here or there for more highlights. Maybe use a
gradient or two to play with it. Play with the modes
of the copy layer. Addition seems to enhance the gel
effect. Multiply doesn't look like gel but is
dramatic. Burn is a really cool effect. Soft light
works great with this too. Difference looks like a
color negative. Value gives a strange op art effect.
I like being playful.
Patrick