On home page, the tool tip using JavaScript or any other scripting methods may be helpful in an user's perspective, but not at all helpful in an SEO perspective. This is followed by many websites that are re-designing their sites in terms of usability of the website.
Further more, on home page, there will be maximum number of images covering keywords either through
CSS or through image. Even this will make the age old SEO a futile effort if at all a site is SEOd and finding ranks on Search Engines. IMO, all the remaining images containing texts need to be replaced to text.
In addition to this, while re-designing a website in an SEO perspective one should consider retaining the page names as they were before and is a concern only when the site is already ranking well in Search Engines.
Finally, all the required
301 redirections should be on place when there are chances of renaming or considering deletion of existing pages and to avoid mistakes Customized 301 is the best bet.