For the top menu you can try something like this ... its not as concise as it should be, for that you really need to restructure some of the css. It also does not use sprites, which it really really should, especially for menus. This only does the home button, you will need to add for the others as needed.
#main_menu .listlevel1>a:before {
margin: 0;
margin-right: 0.5em;
position: relative;
top: 4px;
display: inline-block;
z-index: 5;
}
/* home button, repeat this for #button_forum, #button_pm, #button_admin, #button_unread, #button_unreadreplies */
#button_home a:before {
background-repeat: no-repeat;
background-image: url(../images/board_select_spot_child.png);
width: 16px;
height: 16px;
content: '';
}