Hi,
I use the Fugue icon set (pinvoke.com) but i’ve come across a few scenarios where the icon combination (such as image+printer) isn’t already created..
To solve this, I created a neat little script that does it all for you - just click on the two image (main + small) you want to combine and it generates it for you to save.
http://richardlyon.co.uk/fugue/
Enjoy, and let me know if it helps you!