To be honest I was rather surprised when I saw the "scottish armour" from With Fire and Sword, I guess I shouldn't be as tartan is the easiest visual way to show they are Scottish I guess.
I mean tartan trews (and jackets) were worn but so were a lot of other things depending on use, cost and availability.
The more muted earthy coloured ones like in that picture are okay, but the full on bright red "Stewart" tartan probably isn't very in keeping with what a regular foot soldier would have.
Also the caps/bonnets in WFaS are good , they go with any of the more generic armours to add a bit of a Scottish touch to the visuals.