It can be either, but in general people are more likely to say "is" than "was". If you use "was" you're emphasizing that he is no longer alive. Otherwise, you can say "is", which doesn't have any particular emphasis and therefore is more widely used.
You can say "is" because this is a photo of Michael, and it still exists, and he still exists as a photograph.
You can say "was" because this photograph is am image of Michael, and Michael unfortunately no longer exists.