Vanilla in Creme Brulee??
Go get a vanilla bean if at all possible. If there's a Penzey's near you, they have them and they have really good ones. If there isn't a Penzey's near you, try Cost Plus World Market, Whole Foods, or a local high-end grocery store. The depth of flavor you get from a vanilla bean versus vanilla extract is dramatic, and it's worth the extra cost of the vanilla bean if you want a truly knockout creme brulee. That said...
You can substitute 2 to 3 teaspoons of vanilla extract for a single vanilla bean, I'd likely lean toward the stronger end of the spectrum.
Or you could give a splash of vanilla extract to pick up the flavor of your real flavoring, such as orange zest or a layer of mini chocolate chips on the bottom or some better things you could think up. Creme de menthe? Dolce de leche?
Additional thought - I wonder what would happen if you stirred a ribbon of orange marmalade through the Creme Brulee just before baking.