Den Wall,Flooring & Windows

I am going to remodel our den. We have on one wall a 5' window, the other wall has a greytone stone fireplace, and then the opening. We have a chocolate brown microfiber pit. What wall color do you recommend, for the floor would a multi color carpet be ok, & for the window should we get verticals, & what color? Also, would red pillows & accents go. Thank you so much for your help