i like the last one the most.
i like that the big rock is roughly in the "ratio" 1:1.6 that gives a good place for the eye to rest on. i would run your ground cover all the way to the back wall in the dead space. then make your background plants create a V shape with the point of the V being the ground cover on the back wall and getting taller as it goes to the sides. this is just my opinion....hope it helps