A couple of observations.
This isn't a studio photo as he's standing on grass against
a plain backdrop so taken outside somewhere.
Also he's not wearing the usual Scottish style tunic, see below.
It may be he is from one of the Scottish Regt's. who didn't wear
kilts such as the KOSB. They had tartan trews but I believe they had kilts as no.1 dress.
but I'm willing to be corrected on that.
Doesn't bring anything to the party but I thought I'd add it.