I made these icons with just three images. The trick is to make transparant PNG files, and let a CSS background do the colouring. Here are some examples, with a blue, a black, a red, a yellow, a grey and a icon with a random generated color. I've resized the used image to 16x16, 32x32 and 64x64 pixels. Go back to the article.
This is how it works:
16x16
32x32
64x64
SEO Friendly
Final (with hover and link and seo friendly):
You can also use this technique on a black background, or every other color. You just need to edit the image first to make the rounded corners your specific color.
32x32
Unfortunately, it's not possible to use rounded corners here. But they still look good as a square, don't they?
Background from: http://www.cgtextures.com/