Here's a quick tutorial on how to do these icons / use
my brush set, because several people have asked
First of all you need my circle masks set *
click* ... I'll get to the "do it yourself" part later on.
#1 Now you work on the image you want to have showing through the circles, just like you do with every other icon. I think coloring tutorials are mostly useless since the result depends so much on the picture you use, so I won't bother, but I increased contrast and used scratch texture on some of my icons. Let's say your icon looks like this now:
#2 Add a new layer on top and fill it with white (we all know how it will look like now, right? ;-) ) - change the layer setting to "lighten" (you won't see a change)
#3 Load your mask brushes, select black as color and use the brush on the white layer. Your icon should now look something like this:
#4 Alternatively you can use the mask brushes as eraser - I do this if I don't want the top layer to be white but a different color or a texture. In this case the setting of the top layer stays "normal"
#5 Now the DIY method for the circle mask brushes. I just used the standard round brush (hard outline) for these and played around with different sizes and different shades of grey and mostly black. The lighter you get the less your background will shine through.
normal top layer =>
=> set to lighten =>
I hope this helps - I threw it together really quick and didn't check spelling.