On Light and Lucid 4.3.0:
Original:
Main.css
#header .line1 .logo a img {
height:48px;
width:203px;
}
Customer/head.tpl
<div class="line1">
<div class="logo">
<a href="{$catalogs.customer}/home.php"><img src="{$ImagesDir}/xlogo.gif" alt="" /></a>
</div>
MY CHANGES
#header .line1 .logo a img {
width: 200px;
height: 60px;
}
<div class="line1">
<div class="logo">
<a href="{$catalogs.customer}/home.php"><img src="{$ImagesDir}/abeezcustom/yourlogo.gif" alt="Way Hay A Logo Change" /></a>
</div>
Hope this is what you mean, works as it should