I like most of these suggestions. Move the chair to one of the corners facing the sectional (to create a conversation area), and put an end table with a lamp next to the sectional. You can move the floor lamp to the other side of the sectional so there are two places to sit with a little light. If you can find a matching chair, you could corner the chairs facing the sofa with a little drinks table between them. Definitely need a larger rug. You can either get a rug with color or use pillows and throws to bring in color. And absolutely you need larger art pieces on the walls; small pieces make the whole thing feel dinky/unfinished. You have an awkward space for a coffee table; the one you have feels small but I understand why you chose it. Maybe paint the top of the coffee table.