welcome to the wonderful world of mapping, bob!
you have a lot of good ideas, some of which are more outlandish than others, so i think that this :
I'll start after I get finished with a few regular terrain based maps.
is probably your best way to get acquainted with the way spring maps work.
the map you posted pics of; which i would label "luke i am your father" due to its tubular death starry nature, is very cool, and makeable, just some of the parts of it will be a bit hacky.
having it suspended in space for instance isn't too hard; you can use "voidwater" to alpha out the water textures and anything underneath it; and then create a skybox using your original model, you'll be 90% of the way there.
the problem is that the skybox is difficult (impossible?) to perfectly sync with the map... so as you scroll around; the sky will appear to stay in the same place. maybe having the floating area held in place by forcefields would work better as a concept than having it direcly attatched (although i must say it looks very cool in your concept)
try making a "simple" terrain map first and learn the ropes; then give some of these avante garde ideas a go. if you need a hand with mapping in 3d max; either me or picasso CT can probably help you out.
natural terrain is the most popular theme for a spring map but by no means are the limits of what can become a spring map dictated by this.
theres a thread in the mapping forum called "mean streets of the deathstar" that you may want to check out; its sort of a progress log of me trying to make a city map in 3d max, there may be important information to be gleaned there.
cheers, welcome, and good luck!