The sad part about search engines is that they cannot read images or text written on images. But they can pick up alter texts. What you can do is develop seperate pages that have valid content related (also keyword rich) to your website, like faq's, articles etc and give links to the frontpage from those pages. These pages are sure to rank well in search engines. Although don't do too much of these pages. These pages are also called doorway pages; but they won't be penelized until they provide valid information and are in moderate propotions.