About those three pipers, as the caption says they're the men that came in 1st 2nd and 3rd in a piping competition. The man on the left appears to be a military Pipe Major, the man on the right in the uniform of a civilian pipe band (many of which wore uniforms very similar to military uniforms) while the man in the centre is wearing ordinary civilian Highland Dress of the time, a Regulation Doublet, long hair sporran, etc.

It was, and still is, quite common for pipers to "dress up" a bit and to wear black jackets with silver buttons during the daytime.

In fact most pipe bands nowadays (the ones that have jackets) wear black Argyll jackets with silver buttons at all their competitions, which take place at Highland Games during the day.

At the time that photo was taken it was quite usual to wear long hair sporrans with civilian Evening Dress... and it's fairly common nowadays too.