Really sad to hear the news mate. The only thing you can take from it is that he passed away at home and in his sleep, you did not have to go through putting him down.
I have been through that once and it is awful. The time is approaching again soon as I have two 14 year old dogs (sisters from the same litter who have always got on!). The kids have grown up with them so it will make it even harder.
As with you, we have had so much joy with them over the years and they leave a massive hole. I think I may have a break from dogs for a while after these two (but I said that last time....).
Great photo by the way of your old boy.