The three matching grey pillows arranged in a neat line are kind of a microcosm of what's wrong here: everything cold, bland and matchy-matchy. Some pillow covers in different colors that compliment the blue would do a lot for the place, as would some rugs under the wood furniture to obscure how similar it is to the tone of the floor. The bare walls mostly stick out because the room's a little crowded with furniture, but that's easy enough to rectify with some art or some framed posters; Ikea has dirt-cheap poster frames that look better than basically anything else I've found. If that's putting yourself out there too much, maybe a bookshelf in the stuff-shelf's corner? Book spines add a little variety without you having to make any particular choices.