Winter + fireplace = ahhhhhhh. While most SF apartments aren't equipped with such a comfort, a small tabletop, floor, or wall mounted option can offer a bit of warmth and a great visual.
Table Top Fireplace by Gido Wahrmann for Carl Mertens
Blomus "Vidro" floor fireplace
Blomus "Chimo" wall mounted fireplace
Table Top Fireplace: http://www.gnr8.biz/product_info.php?products_id=29
Vidro Floor Fireplace: http://www.blomus.com/blomus.php?l=en&a=detail&i=65331#i65331
Chimo Wall Fireplace http://www.blomus.com/blomus.php?l=en&a=detail&i=65185#i65185