Painting and rug. I think the corner shelf will be too much. Also - maybe a new light fixture, or lower the one you have. Have you tried turning the table (short side facing windows?)

I think the painting will be a good size, but would skip the shelves. Plants? Maybe, if they are substantial and not little undersized ones on the floor. A rug would be a great addition and would lighten things - your table and chairs are fine.

Do you leave the shutters closed all the time? If privacy is an issue, I might look at bottom up shades that could be closed enough to block views into the room but the light and view out could happen above the tops of the partially raised shade. Or get a split shutter so you can keep the bottom part closed and open the upper for light and view out.

I, too, would try the table the other way - I think Sammie means long side facing windows as it looks like the short side is facing the windows now.