I've noticed this steady progression in Brian's pictures over the past few years, he's starting to look more and more like he did when the band was first formed... It's mainly in his 'childlike' mannerisms, and his facial tic where he talks out of the side of his mouth. It's fascinating to me.
For instance:

This image is from Brian's facebook page, yesterday, it likely was taken in the last month or so.
Here's a similar expression from wayyyyyyy back in the day, he looks nearly exactly the same sans a few wrinkles

I think he's reached a time in his life where he's more content than he's been in years and it harkens back to how he felt in the mid 60's.