There is a common joke about people who are very advanced in their career (and their life) and are still using an old picture from the early days of their career.
The picture on my webpage was taken in April 2011. I was 26 back then. I am not much older now (do the math if you want to) and I have no gray hair yet.
So if you want really old pictures, here is one from during my PhD, I think it was Christmas 2008. An older one? The one from my French driver's licence. I gave an old picture, I was 15 on this one. An even older one? This one was taken during vacations in February 1987, I was 2 year and 3 month old.
But as long as my hair does not turn gray, I think the one from 2011 will be fine and give a realistic idea of what I look like.