ETA: Feralpeg, I am just now seeing your photos come in. NICE JOB! I like the clean light/white with the pop of red. The silver stainless in the kitchen really works great.
OP, I have a greatroom, open floor plan, but with a separate kitchen. There is a nice 4 ft. framed doorway, so semi-separated.
What kind of style and colors would you like to see?
Have you looked thru home magazines?
I don't have a lot of actual Decor... and with an open space, you just don't have the wall space.
I would come up with kind of a color and design theme, and start working from there.
Light open airy colors??? Some warmer tones??? More casual or farmhouse??? More simple modern clean lines???
Once you have decided that, then look at your space and think about how you can break it up, organize it, direct the flow.
You can use things like shelves, floor lamps, mirrors, drapes, etc...
If you could manage to post a couple of photos, that might help!
If you are not sure how to do that, just upload them from your computer to any public photo site. I have Shutterfly. Then you copy the address link, that actual computer-eze link to the photo location, when you click the add 'image' there at the top of your post here on the DIS.