Background Images as List Bullets
 

ul {list-style: none}
ul li {
background-image: url("path-to-your-image");
background-repeat: none;
background-position: 0 0.5em;
}

You can use try this also,

li {
list-style: none;
background: url(bullet.gif) no-repeat left center;
padding-left: 20px;
}

some of the web browser not supporting this one.

Also you can try to do with this

#content ul.bullet li {
list-style-type: none;
text-align: center left;
background-image: url(../images/ex-list-bullet.PNG);
background-position: center left;
background-repeat: no-repeat;
padding: .3em 0 .2em 1.1em;
}

#content ul.bullet {
margin: 0 0 .3em -.5em;
}