Opinion:

I would agree about a solid colour vest on most people. On a gent of some substance the vest with the diamonds does give a "slimming" effect on the outfit and does that well for you. With the vest that you are wearing, I would offer up the idea of a brighter choice of hose colour to return attention to the tartan.
The photographer was quite close to you. The view of you in the photo is what I would see if I was close enough to you to carry on a conversation. The display of your left leg indicates the hose are probably at a reasonable height.

You look quite comfortable, and like Jock, I do not go for the matchy-matchy thing. More variety may even slim another stone off in the outfit.