Going from blonde to dark, how do I prevent it from looking unnatural, but still make it eye-catching?

I have fair skin, some freckles, and grey eyes. My hair is naturally (ashy) dishwater blonde, but I have been wearing it for a long time heavily highlighted to a much lighter blonde. My eyebrows are light brown, very ashy, and I have no intention of colouring them.

I would like to colour my hair as dark as possible, I’ve worn it dark many times over the years, but in my experience brown hair dye can come out looking very boring. I don’t look good in warm shades, so auburn and reddish browns are out of the question. Could I go very dark with some lighter brown highlights to add interest, or am I going to be stuck with “drab” if I use an ash brown, regardless of what I do with it?
Photos are welcome and appreciated. Again, no red or auburn, please.