Well the good news is that your room is really limitless and looks like it has great light to it.

Looking at your comforter (kudos btw, we have the same one), I would say that because of the busyness of the pattern, I would say you need simplicity to balance it out. Also, from your picture it looks like the wall with the headboard against it doesn't get too much of that light.

My initial idea would be to place the bed against the wall opposite the two windows. Against the wall where the headboard currently is, I would get two or three of the Mongstad mirrors from Ikea, equally space them out against the wall, and let them be free-standing tilted up against the wall. Not only does this create a rhythm, the scale of them will make the room feel larger, it ties in the black from the comforter so it is not just the tv that is black, it will help cast light across the room, open the space up, and create new perspectives due to the slight tilt angle. This energizes that wall and reaffirms the significance of the bedding since it will be seen in the mirrors. With this scheme, you can place the radial mirror you like centered on the wall between the two windows to treat it like art. The radial mirror placement here will also draw attention to it since it will be a focal point when entering.

If you like the headboard where it is, I would remove the headboard or make it shorter (DIY or replace with shorter one) and place two of those mirrors I mentioned earlier on either side of the bed as shown in the second image. The as-is height of the headboard coupled with its dark color would make it compete with the monolithic mirrors. I would even go so far as to lower the bed if possible to make the mirrors seem taller. The result of this creates a nice open display space that is framed by the height of the tall mirrors being on either side. In this framed space, I would place that radial mirror, perhaps with downlighting over it. The key to the moves in this second idea would be lowering the headboard/bed height and having symmetry (I would be adamant on the bed being placed exactly center on that wall with the mirrors being symmetrically placed on either side.). This evokes balance and order in every sense of the word.

Regarding color scheme: You have a multitude of options. Keep the lavender walls and accent it based on the feeling you want. A lighter lime green would work well in spring, and perhaps some red or varying shades of purple in fall / winter for warmth and romance. Regardless, use pillows, throw blankets, a rug at the end of the bed, curtains/drapes, and accessories to bring in the accent. These things can easily be changed with the season and are fairly inexpensive if you keep an eye out for sales.

I'm thinking a variety of light lime colored accents, coupled with a fresh white calla lily in a simple clear vase on a nightstand would look modern, yet elegant. Get some soft white semitransparent window curtains, pull them to one side, away from the center of the room, with a simple rope & hook about 4' high and you're good to go.

Anyways just my two cents on it. Have fun! Play with it and see what you like. Those are just my initial two thoughts on how to utilize those items you listed and create a nice yet simple modern space.