Greetings Young Kiwi Jedi
Andy--you've been busy! Good concept here and the layout looks balanced as you have it now.
Some no cost ideas could include a placing a simple wood power pole (with crossarm) on the corner edge of the dio near the rear end of the Sherman.
Roof details always look good so you could take some plastic tubing and place short pieces of them on the shed roof as pipe vents.
This might be too late, but a window or door opening in the shed would add some interest to the structure.
Weeds grow everywhere, so you could consider tucking some small green foliage all along the base of the brick wall.
An old pile of well weather lumber could be stacked along the inside of the brick wall near the deuce, or, your could place a small pile of lumber/debris on the corner near the back end of the deuce (behind the interagator). This would balance out the power pole placed on the opposite corner.
Just some thoughts for you Lord Kiwi, --- good to see you attempting another dio.
The "Force" is strong in this one.
Signed
Charter Member Kiwi Fan Club