In /skin1/customer/head.tpl replace this
Code:
<div class="line1">
<div class="logo"><a href="{$catalogs.customer}/home.php"><img src="{$ImagesDir}/xlogo.gif" alt="" /></a></div>
with this
Code:
{if $main eg "fast_lane_checkout"}
insert new image here
{else}
<div class="line1">
<div class="logo"><a href="{$catalogs.customer}/home.php"><img src="{$ImagesDir}/xlogo.gif" alt="" /></a></div>
{/if}