Get black so that you and I can do a full interior swap when I get tired of my bamboo
Seriously, I'm waiting for my Le Mans Blue + Bamboo + Carbon e90 M3 to be built. As you can see from my posting history, I was having trouble picking an interior color too. My current e46 330i ZHP's interior is all black leather and I wanted a change. The bamboo has a nice warmth to it, that I like. Like you my exterior is dark, so a contrasting interior seems more appealing to me than more dark inside.
Also, it depends a little on what look you are going for. I'm not going for a street racing badass look, so having a less aggressive interior isn't an issue for me.
My advice is to look at a lot of pictures (should be no shortage of JzB with Bamboo and black interiors) and see if that helps you. Otherwise, flip a coin. In the worst case, you have to do a full interior swap with someone else or bought parts and you're out a few thousand dollars. Small price to pay for a car that makes you smile every day.