I think your leather evokes coldness, you need to break it by adding lots of texture... I would look at cushions that are either soft and fluffy in the winter or satin sheen for the summer (regardless the colour you end up with)Whatever carpet you end up with must be something that invites you to rub your bare feet on it and feel cosy....Also consider painting your walls a darker colour - you seem to have enough light from your window and the sofa will bring light.In this image do you see how the cold white leather has been broken up with organic elements and fur cushion... take a cue from this design...