Some ideas:
The desk looks really good, you just need something above it. You could get a TV cabinet to give heights to the desk area. You don't have to center it on the wall if you build a cabinet with two large cubbies, one for your monitors and the other for the TV. (image attached)
As for your art work it is not to big for the space, but remember to balance it the other items in the area. You don't want a crowded corner and then long expanses of nothing. Ceiling fans come in all styles and sizes. Find one that matches your style may take some hunting but you will find one. I'd go with something more modern, see if you can't find something in black. The size depends on the rooms dimensions and the style. Some fans, for living rooms and bedrooms can be larger, up to more than 50 inches. If it's a big space than a large fan won't look overwhelming, but getting one that is to small may look worse. Fans with lights are useful but remember your decor, there is really only two kinds of lights, the single globe and the multi-globe. One produces more light, but you can also see the light bulbs, though that model is easier to change a burnt bulb. If your fan is not where you'd like it you can get an electrician to move the junction box, or just use the current location. A Fan with light has the added benefit of air circulation versus just a light fixture. While the latter can be more stylish, ceiling fans can cool off the space without having to turn on the air conditioning.