Icons can make your website look super cool when used properly. My preference is to use icons that are exactly 16 pixels by 16 pixels. That’s just about the height of a line of text so the images line up well with words. I am a huge fan of Mark James’s “Silk” icon set that you can download for free from his website at famfamfam.com. Dan Cederholm also provides very nice icons for purchase at his Icon Shoppe. Go nuts.