Image Links Pass the Same Weight as Text Links
Provided you have alt text on the image, which is equivalent to the anchor text, image links should be treated the same as text links.
There are no limits to Link Titles, Image Titles and Alt Tags
Title Attribute on Links is Ignored
Google ignores the title attribute in anchor links, but does use alt tags for images inside a link.
Image Alt Text Adds to the Page Content
Adding alt tags adds content to the overall page.