Nice choices! I would first pull your sofa and chair away from the walls and on to the carpet to make a more cozy conversational grouping.

Gallery walls are tough to pull off. It's difficult to get the scale correct and to hang them properly. They look great in magazines but ninety percent of the non professional gallery walls shared on Houzz look off.

Here is a good article about choosing the size of your art. Proper size painting

I like the idea of a landscape in your space. The sky, water, trees will work nicely with the teal and the natural look of your rug. What types of art do you like?

Will you be purchasing a coffee table? If so I would buy something large that fits the wide open space.

I love your home and the furniture is fabulous!

I read the article that d_gw linked to. Maybe the sizing proportions have changed, but what is suggested in that article seems small: a 44 inch wide painting on a 120 inch wall.

I linked the article because I liked 75% of the sofa advice. SF Gate usually gives good decorating advice so I didn't analyze the rest of the article. I am horrible about imagining spacing without examples so the other advice may be off, I have no idea. Thanks for pointing it out.

Or less contrast if you use drapes color for frames.

Art is very personal and no one can tell you what "goes". Your heart has to tell you that. Go on a site that sells paintings and see what really appeals to you. I really like the large painting since it harmonizes with the drapes, which take up quite a bit of room and will seem more integrated if the art echoes that tone.

Your room is wonderful. I think celerygirl's examples show you how well 3 totally different styles of art can work beautifully in your space. I think the trick will be making sure whatever you do on that wall is large enough to have the impact she shows in her pics.

Love the rug.