For what it's worth, I think it will look fine. The black 'Shadow Tartan' is plain enough to look plain!!

When it's cold enough for a scarf (not yet this winter, but things they are a'changin' next week according to the forecast!), I wear tartan scarves with my plain kilts, and plain scarves with my tartan kilts - always aiming for good colour co-ordination of course!

The only time I'll wear a tartan tie is with a plain kilt - same principle.