I like the most recent layout that you've done the best. When you don't have a ton of stones to work with, it can be difficult to get a layout that you really like. I think you're onto something decent here, keep up the good work.
One recommendation that I have and found that helped me a lot with becoming more satisfied with my aquascapes was to mess around with the slope a lot. Try to create some movement from one side of the tank to the other. Maybe try to pile up some of the substrate around where the stone is to make it seem as though it continues underneath or perhaps lower the area in between the two prominent stones a bit, so as to draw the viewer's eye there even more.