the default logo for this theme in skins/MisterLarry/images/roundcube_logo.png but if you set logo in config/main.inc.php ($rcmail_config['skin_logo'] = '';) I'll just ignore the default logo.
I prefer keep $rcmail_config['skin_logo'] = ''; blank and change the skins/MisterLarry/images/roundcube_logo.png
btw, thank you very much phireware for great theme