Joe McG, there are many sources of free icons such as click here, however when I wanted an icon for my desktop to represent my digital camera files, I generated my own using a bitmap editor (I used Corel Photopaint, but any other would do). I generated a bitmap of 32 x 32 pixels. It is important to use all the pixels even if some of them are not needed, otherwise the image gets stretched out of shape. I then saved the bmp file as filename.ico. I selected the Windows generated icon, right clicked and selected properties. Clicked on the "Change icon" button, and navigated to my new icon.
Generating the new icon wasn't difficult. With only 32 x 32 pixels, great detail wasn't necessary. I know some professional icons have fancy features like transparency, but I haven't worked that out yet.