If you sell anything put it on a entry table or a floating shelf it would be nice to display the products or some books

A simple way to get a great background is to create wainscoting with paint. Here’s an inspiration pic, and a mock-up of your space. To create a crisp line, after carefully applying painters tape, paint over the seam with your current wall color to form a seal, then your new paint won’t seep under the tape.

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I was thinking I’d like some type of shelf/shelves to put knick knacks on or a small plant, but I’m not sure that it would look right. I think it would have to be above something like a narrow table of sorts, or it might look odd. I’d like to get rid of the posters.

Something similar to this would be an inexpensive way to fill the wall, and could be reconfigured as you add pieces. I like happylegs idea of displaying books, weights, etc., even if they are not for sale. If you are on the floor when you zoom, lower the shelving and place art above.

I came across this idea and I like it

I don’t want to take up too much floor space either as the room isn’t very big

Since you already have a nice bookshelf you really don't need that kind of storage so what about taking down the posters and applying a peel-and-stick wall mural? You can find them pretty inexpensively on amazon, and a bit more pricey on etsy or wayfair. There are so many designs available that I think you'd have fun choosing the one you'd love in your room.

I think you just need some pretty wall art, and a nice area rug. Might want to consider a different window treatment as well; the lace is very delicate. (Caveat: I don't know your taste, I just grabbed some pics that seemed like they would make a good zoom background, and a rug that kind of coordinates, to give you the rough idea.)

Yes I was thinking of changing the curtains as well.