I would almost GAR-ON-TEE it's a fashion tartan (specifically, a blue toned variation on Dress Stewart).
I don't have full access to the Scottish Tartan Authority (not a member, based on present budget), so I can't say for certain.
Yet, I'd bet money it's a fashion one.

However, I REALLY like it. It has nice echos of the Scottish flag and the Stewarts in the same pattern. Where did ya get it?