Get some more throw pillows for the sofa in a complementary color from the purple pillows. Perhaps a golden yellow or a sage green. The space needs a little brightening.

Ha! Well in that case, pick some brighter colors to offset the all gray scheme. Teal, dark blue, aqua, even orange might be nice.

I think a rectangular glass and metal coffee table would look best. But if you want the ottoman to put your feet on, get a rectangular one so you have room for a large square tray for drinks, etc. Or consider a rustic wood table. I would also use very narrow (12") end tables at the open end of the sofa and between the two chairs.

I would pick colors for throw pillows from your FP art

You need strong colors, like the teal and terra cotta in your first inspiration photo. The other ones are all too pale and don't change the overall pale look. Try yellow, aqua, green, brick red - anything to bring your otherwise nice room to life.

Teal might be good, but you do not have anything teal in room. I would get rug with some color and then pick color from rug for accent pillows. Shag rugs are out already.

I think white or off white textured pillows on the sofa would be nice or as celery girl mentioned, tones similar to your art over the FP.

I agree that fluffy white or soft gold pillows would look great while still keeping your room neutral.