I'd suggest dark red curtains if you need curtains at all -- the windows are beautiful as they are, and I'm not sure whether some kind of blind might not give you the ability to darken the room when you want to. On the wall, if you are real fans of any movies or TV shows, three big posters would be fun. Otherwise, I would still suggest using three pieces of art there of that size, all equal in size and somehow relating to each other. Three floral works, or three works in the same style, perhaps. I think a large plain textured rug in a light neutral from one of the cushion fabrics would tie the space together well. You might also consider a lovely low coffee table on the rug to lay out your snacks and drinks for serious media nights.

Instead of the solid grey, you can go for sketches in grey with flashes of mustard/ yellow. Or, look up these links for wallpaper ideas https://goo.gl/images/OrCtY1 https://goo.gl/images/0ZpAmU

Depends on what effect overall you want -- hot tropical feel (oranges and reds) or a bit more toned down? You can take inspiration from pictures of gardens with lime green heuchera or sweet potato -- often paired with chocolatey purple, silvery greens and blues.

Though I voted for the wood panels Its not the always that case it depends upon design to design. To choose any one will be injustice for other design.