I too like the overall color scheme of your tartan, but feel it lacks something----bold. Most tartans, other then those based on the black watch, generally have something about them that is a bit bolder than the rest----a yellow or white accent stripe, 4 sequential red stripes, etc...

I am wondering if widening up the red and blue strips just a bit, and maybe the whitish field on which they center, might change the feel enough to bring some boldness into the design. just a thought.

Good luck with it.