You are right to go with a coloured shellac on the walnut. It needs something to give it a bit of warmth, especially AB Walnut. You can also use a touch of dragons blood and/or alkanet root. Probably less is more. With alkanet I've had walnut looking like Indian rosewood, which is taking things to an extreme. Lemon shellac just results in an insipid look, something more towards red helps.
The rosette reminds me of the larger rosettes that became prevalent in Spanish guitars, late 19th century. They make for quite a strong bold statement. You've kept away from multi colours, which is a very good decision in my book. The only thing I'm not fond of is the plantilla. I find the upper bout to be of the sloping shoulder type. That's just me, some may like that effect.