Last up, the Large build category. This doesn't really fit on this blog, since these aren't really the sort of creation I highlight here, but for completeness sake I'll just mention my top 6 quickly.
Mariann Asanuma's Dr. L. Ego's Laboratory. That central structure is beautiful, especially the curving staircases. I do think the plain blue baseplate around that is kind of empty, though. The upside down goblets as erlenmeyer flasks is really clever.
Lt. de Martinet's Charles' plans is pure steampunky goodness. My favorite bit is the drill machine coming up out of the ground. Also the guy on the balcony on the left firing some sort of rocket at the small balloon.
SirNadroj's Der Geist's Roboter has some clever parts usage. I particularly like the helmets as kneecaps.
Karf Oohlu's lunatic's lunar lair was my favorite from this category. Everything is top-knotch, from the treads used on the walls, to the floating head, to the monster under the trap door. Flawless.
Tiberium_blue's Dr. Monochrome's Monodome. Was my other favorite. The idea is funny, and the curved wall, the robot, the green turning to black tentacles are all great. Mom bringing down snacks makes the scene, though. Only complaint is why does Dr. Monochrome have a yellow head?
Nolnet's Doctor Dank's secret underwater hideout came in late, so was not up for judging, but it's great anyway. Clever use of the X-pod cannisters, the unique shape, the little underwater touches (e.g. the diver, shark, pirate skelly) and Dr. Dank himself are all great.