You want to use padding on your link, this will leave the background where it is but move the text, try padding-left: 25px;
. But adding padding will add to the width so you will want to adjust the width of your link and reduce it by the amount of padding you have added (maybe not in this example)
Also your example image isn't loading
Try this:
#maincontent a:link {
background: url(images/css-images.png) no-repeat top left;
background-position: 0 0;
width: 4px;
padding-left: 25px;
height: 12px;
display:inline;
}