Your warning picture is very nice, but it's better make it less picture-ish. See, the right part of the picture can be easily made of HTML with some styling. This way we can customize it's text. I already made it, so will just share it wish you.
Change your picture to the one attached and the corresponding line in controller to this one:
return '<div style="float: left;"><img src="' . $qs->www . 'images/warning.png" /></div><div style="height: 37px; width: 400px; padding: 15px; border: 1px solid #e5db55; border-radius: 4px; border-left: none; margin-left: 65px; background: #fefccb;"><span style="color: #878314; display: block;">Warning</spam><span style="color: #404040; display: block;">Please, <a href="index.php?option=com_simpleregistration&view=registrationform&Itemid=115" style="color: #ea6d40;">login first</a>, if you would like to make a pirchase.</spam></div>';
Also text is better be placed in the language file. Hope it'll save you some time.
Attachment warning.png not found