How about this...
{if $main eq "catalog" and $current_category.category eq "" and
$smarty.get.mode ne "subscribed"}<img src="{$ImagesDir}/custom/logo_splash.gif" alt="Tracy Porter" border="0" width="480" height="49" />{else}
<img src="{$ImagesDir}/custom/logo.gif" alt="Tracy Porter" border="0" width="480" height="49" />{/if}