The beauty of LEGO is that it's designed to be modified, to be changed around. I'm usually not content leaving my sets built according to the instructions, and often modify them and build my own creations (known to the LEGO customs community as MOCs) out of spare parts.
I think it's a big pity that LEGO looks like it's selling out now - boxes are far larger than the unbuilt sets contained within, and some of their newer licenses are very hit-and-miss: I suspect the LEGO company is still recovering from the losses incurred with their unpopular Prince of Persia movie LEGO sets. As my Dad says, the spirit of LEGO shouldn't be this commercial. It's about making things from components, creating something from a pile of "nothing". "Scratch-built" means that the MOCs are created from spare parts, not from an official set.
|Wampa Cave from Star Wars Episode V: The Empire Strikes Back. Built from scratch.|
|Luke Skywalker and Darth Vader's lightsaber duel, also from Empire Strikes Back. Built from scratch.|
|Ewok Ambush. Many of the custom creations I build aren't direct representations of actual scenes or vehicles in the movies. Scratch Built.|
|Attack on Snowspeeder Bay. Snowspeeder modified from official LEGO set, maintenance bay scratch-built.|
|Naboo garden battle. Scratch-built but includes components from official sets. This is the one I'm the proudest of, actually.|
|Venice Catacombs diorama from Indiana Jones and the Last Crusade. Scratch-built|
|Indiana Jones ravine swing. Scratch-built|
|the Batpod from The Dark Knight. Scratch-built|
|The Tumbler Batmobile from Batman Begins and The Dark Knight. Scratch-built|
New folders may take some time to become "public", ie approved by the Brickshelf staff.