Go from this:
I'm not too sure if it's translatable, it's been some time since I've used GIMP and or PSP. It might be? There's no selective colouring, curves, or anything like that; just some layer masks and textures. :) Beware, it's image heavy! There will also be a quick tutorial on layer masks, for those who aren't familiar with them (since they're used a lot in this tutorial)
1. First off, duplicate your base twice. The middle layer should be set to Soft Light.
turns to .
2. The top duplicated layer should be set to Overlay.
Now, the overlay and soft light makes it REALLY BRIGHT. I'm not fond of really bright icons, since they tend to hurt my eyes, so we're going to even it out a little bit, and mute some of the colour. SO! To do this, I used this texture:
(it was used in a tutorial by gavinnerism, as well as the second texture in this tutorial, which is where I got the texture from.)
Place this texture between your background (base) and first duplicate layer, and set it to Linear Burn.
Not much of a change, huh? Not to fear! Take this texture:
put it between your second and third duplicated layers, and set it to Luminosity. Bring the fill percent down to 75%.
There's now a big white splotch on her face. :/ Here's where the layer masks come in.
For those who have never used layer masks, or are unsure how to use them if you've at least clicked the button on your Layers toolbar, you'll want to keep reading.
For those uncertain of where this magical option is, it's here:
You'll notice, once you hit the button, that your colours palette turns black and white. Yes, this is normal. :) When you use a layer mask, your palette turns greyscale. It works as an eraser and a redo tool, in a way, only less messy, and less annoying. Ever wonder how iconmakers kept the colour of one thing in an icon while everything else was either muted or completely black and white? Layer mask, I would guess.
A layer mask is just what it sounds like: a mask for the layer. It erases what you don't want on the layer you're working on, instead of erasing EVERYTHING through the layers you just worked on.
To use a layer mask, you need the paintbrush tool. It's simple to use: you draw over what you want to erase in black. If you mess up, or decide you don't want to erase a part of the layer you're working on, you use white. You are free to change colours at any time if you change your mind. All it takes is going back over that area with the paintbrush. You can also use dark to light grey; dark grey erasing not as much as black, and light grey leaving some of the effect in while not returning it completely (if that makes sense).
Also, when you use a layer mask, another box will pop up next to the thumbnail of what is on that layer. That's to see where you're working on, if you miss spots, etc. To return to your normal layer, click the thumbnail on the left, or click on a different layer.
Hopefully this won't become too confusing. :D;
Continuing on; for this next part, I chose a close-to-midtone grey to colour in with. It leaves me with a smoky/foggy effect without getting rid of it completely.
Colour in with the brush around the face...
...and ta-DAH, no more white splotch on her face!
Now. One last texture. I can't remember where I got it for the life of me. :( It's been a long time.
Set this texture to Color after bringing it to the top of your layers.
Well crap! I didn't want it to be black and white. D: So, it's time for another layer mask! For this, I know I zoomed in to 200%, mainly to see what I was doing a LOT better. Here's where it gets fun: for here eyes, I used black. Just the irises. For her hair and the whitish dress thing on her arm, a lighter grey (colour #6A6A6A). For her skin and the background, an even lighter shade of grey (#C1C1C1). Aaaand finally, to get the bottom highlight in her hair to stand out, a dark grey (#474747). If you mess up anywhere, just switch to your white palette and fix it. :)
And you're done! I added text to mine, but you don't necessarily have to.
In the end, this is what the layers palette looked like (as a guide):
This sort of strategy works on human subjects, too!
While I didn't employ the exact same techniques to this icon, the layer mask was abused to keep the blue/yellow shirt while the rest was greyscale.
Hope this was helpful to some. ♥ I'd love to see the outcomes of some of your own icons? :D