I think you'll find numerous proven brown ale recipes, so depending on basic style - American, English, Cascadian/hoppy - you should be able to find one easily. The trick is in incorporating maple syrup, which, being nearly all sugar, is a difficult flavor to preserve.
You probably will want to select a malt-forward, relatively sweet brown ale style, and add the maple syrup as late in the process as possible. If you bottle, this will be difficult. If you keg, you're in much better shape... I would prime with maple syrup and allow it to partly carbonate in the keg, then put it in the cold to hopefully stop fermentation. Force carb the rest of the way.
I could share my current house brown ale recipe, which is a smooth American version, but I don't want to be presumptuous, because I've never added maple syrup. Have you encountered any basic recipes yet that intrigue you, or are you looking only for ones with maple syrup? I think you should start with the foundation first.