Is 'Death' Lingering in portraits?

Death. Everyones fear. Other than the strange ones but we wont go there..

Does Death play a big part in portraits? Does it hold significant meaning? Strange knowings of death in portraiture are as follows..

Holbein - Ambassadors
This painting was created to symbolise everything about being rich. The globe is a sign of wealth, the diary on the bottom shelf signifies being open and honest. But the most striking bit about this image is the smear along the bottom/middle of this image. To the ordinary eye it looks like just an ordinary smudge, but no, look closer.. A bit more.. Can you see it now? Yes its a skull, Pat yourself on the back for that. Well back on track. The skull means death is 'inevitable' and is coming for us all, no matter how rich or poor. We will all be hunted down eventually..
Frida Kahlo - The Two Fridas
This painting to me shows the love for each other. The Frida on the right needed a heart to live, so the Frida on the left gave her the heart. This may not symbolise death directly but in the way I described it, is this 'evading' death? Or will it still come back around?

I think Death in portraiture can play a big part if 'played' correctly. In these two cases it has. People may argue my ideas but listen.. They are ONLY ideas..