I personally have not used Paint to make any of my graphics, but I have used almost every version of Photoshop and Paint Shop Pro. I've seen a lot of questions about free programs, and I'd actually recommend
GIMP. It's free and has a lot of the tools that Photoshop has, minus Selective Coloring and Channel Mixer, of course. If you're looking for Selective Coloring the only program that offers that
that I know of is Photoshop, sorry :/
The only problem with GIMP is that it's a lot harder to work around than Photoshop, but if you're patient and willing to learn how to navigate around it you can easily make lots of pretty stuff. I personally don't use it cause I get easily frustrated and I have Photoshop, so I really don't need it
Anyways, I thought I'd join in on the fun and post a tutorial for you all
A lot of people don't seem to know how to use Selective Color, Channel Mixer, etc. to make really pretty colorings so I thought I'd share
I know some people are fans of intense coloring and stuff, and I'm one of them, so if you think this icon or technique gives you too MUCH color then don't use it
I use Photoshop CS2, so it's NOT translatable, unless you want to see how it works out without the Selective Color, of course
Hokai, so let's get started!
We're going from this
to this
in just a few steps
SPOILER!!: Shia Labeouf Tutorial
So far I've found that this technique works better on darker icons rather than lighter ones--down at the examples there is an icon that was used with a bright base, so you can see how it turns out with lighter pictures. It was a bit more blue than I liked but it was still decent nonetheless
Step 1:
First take your base and crop, sharpen, all that jazz.
I used the blur tool to make the lines in his palm less noticeable.
Step 2:
Next, duplicate your base and set that layer to
Soft Light, 100% 
Step 3:
To brighten things up a bit, duplicate your base again, only this time set it to
Screen. The opacity depends on the image, for this one I set it at 45%, but I've also had it set all the way up to 100% on other icons as well
Step 4:
Create a new Channel Mixer layer by going to
Layer-->New Adjustment Layer-->Channel Mixer. Enter in the following settings for each level:
RED
128
0
-38
2
GREEN
0
100
-4
0
BLUE
-4
0
122
4
That makes our icon a little more blue and brings out the reds in his skin and lips
Step 5:
Create a new Curves layer, once again by going to
Layer-->New Adjustment Layer-->Curves and enter in the following points (yes, there are three, and they're all on the same setting, RGB)
First Point:
56, 71
Second Point:
120, 126
Third Point:
170, 140
So now we have this:
Here is a cap of what your graph should look like as well
Step 6:
Now, the red was a little dark for my liking, so create a new Selective Color layer, by going to
Layer-->New Adjustment Layer-->Selective Color and plug in the following settings
REDS
-100
-16
43
-20
YELLOWS
100
-100
100
0
CYANS
100
100
100
100
NEUTRALS
57
0
-23
-13
And now we have something like this:
The reds look a lot nicer, as do the blues, and look! His tie is a really nice shade of yellow as well
And that's it! You're all done!
As with all tutorials, the settings on each and every step should be tweaked with and changed to fit whatever base you're working with. These numbers are guidelines, folks: you should change them to fit your icon. This tutorial is NOT going to work exactly with every base you come up with.
On that note, I'd love to see what you come up with! Feel free to snag any of the icons, just credit Lissy, and if you use this tutorial, I'd like to know, just so I can see how it works on other icons
Other Examples:
(please note: may have been made with slight modifications to screen and curves layers) 
