4 does look interesting, but I'd have to know more about the setup to decide whether thats really a sustainable layout. From that picture, it looks as if a lot of the plants are just in some plastic mesh, on top of slate, with no substrate underneath for roots to grow into...
i don't think you can really attempt to "go for" any of those scapes. You should find a few really interesting pieces of driftwood and build your scape around them, or just go dutch with maybe a few small pieces of driftwood or rocks to define the midground.
....but if you have to, then I would go with something more similar to #2. obviously you are trying to do something a little bit different here, but to do that you don't necessarily have to have some crazy hardscape.
tank #1 is alright, and seems like it would be interesting in person, but it could have a lot more of that depth that make the tanks in competitions so beautiful. The DW is awesome, as well as the mosses, but with so much driftwood it becomes difficult to create the defining characteristics of YOUR tank.
tank #3 is also good (whose tank is that? I know i've seen the journal for it around here somewhere, but i just can't quite put my finger on it!), and I really like the sloping-up-to-one-corner thing in that tank, but you could make a tank similar to that that slopes up from the front-left up to the back-left AND from the right up to the left, instead of just from the right to the left. That almost gives it the feeling of looking into a tank sideways.
tank #4 is really cool. I think you could break apart a bunch of pieces of slate and silicone them on top of each other so that you can just have a wall to hold the gravel in, but still have gravel for the plants to grow in instead of just solid rock underneath. Then you could have a totally WICKED hardscape AND still have good looking plants. Also, I agree with leaf that some HM crawling around in there would be really cool.