White formal vest?

[Shangas]

This doesn't seem to pass Occam's Razor particularly well. I would assume that it is the contrasting waistcoat shown in some earlier pics, designed to be worn either with morning dress or with a lounge suit.

I agree. I still think this is it's most likely use. That, or it went with a similiarly coloured suit for summer/spring weather.

 

[Chrome]

Doesn't show lot of tie.. would look better with bows.

 

[Shangas]

Ooooh! Very, very, very smart!

Now you've made me even more jealous than you can possibly imagine. You should take a photo with your Panama (is that what it is, on the left there?)

 

[dnjan]

Personally, I think it would look better if the pants were a shade darker, for a bit more contrast.
But perhaps it is the lighting of the photograph.