There are many programs on the web that allow you to create your own icons.
I havent personally used any but some others on here may have. Also try a google search for "JPG to Icon".
I myself havnt come across many free Icons which are free.
And if you do manage to find a site which offers free Icons, you will probably need third party software to use them like WindowBlinds Icon packager .
I've made my own with Paint Shop Pro
Long story short: take any simple pic and crop it to make it square. Reduce the size to no larger than 32x32 pixels, then save it in .bmp format, using no more than 16 colors. Then change the extension from .bmp to .ico and presto! instant custom icon! Attached are two examples in .bmp format.
Tom