I mix brown and black all the time esp since all my brown bags are deep colored so look really good with black.
In the case of your bag, it definitely looks good with the sweater. Go for it!!
__________________ 'Without surface, there is no depth' Current wishlist: Bal Day in EB RH?, Hermes Evelyn in BJ GM?, Mulberry Bayswater in Black? Anya Hindmarch Carker in Black? Which one first?
black and brown looks great together when done correctly. I have the eye for it, since I'm wearing black pants with brown shoes right now. Takes a keen eye though. I've seen some BIG no nos out there.