The Galaxy Explorer (LL 928) is my all-time favorite Lego set. It's just elegant. I have two of them. It's hard to pin down exactly what's so great about this set, but if you like it you tend to love it. I guess it really fired my imagination when I was young.
Like many people, I made lots of my own improvements and variations on it. This is one of the best so far: a much larger version.
First, some photos comparing the original with my new model, from three different angles. (Most of the images on this page are clickable for enlargements)
Comparison with original model.
As you can see, the new model is about twice as long and three times as wide, wingtip to wingtip. Building this thing actually used up almost all of the large grey flats I had at the time.
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Cargo bay detail.
Here's a closeup of the cargo bay showing the "engine" (something I cooked up on the Star Trek theory that it just needs to look hi-tech)
Underside.
And the underside. There's a single giant landing thruster that supports the whole ship. Also note the four detachable robot scouts under the wings.
Airlock detail.
There are airlocks on both sides, above the wings. Each airlock has a door leading to the command deck, a door leading to the cargo bay, and a hatch leading out onto the wing.
Cockpit detail.
An outside closeup of the cockpit. There are six crew inside, with the gunner sitting inside the green bubble on top, which doubles as an escape hatch.
Finally, here are two views of the inside with the top removed. Note there are bunks behind the Captain's chair. Still no toilets though. ;)
Interior detail.