I've made a small diorama for "Battle of Endor" (set 8038 - see last picture) and created some big trees for this. Someone asked me for a building instruction, so I made it with LDD.
The set includes the redwood, a small tree, some little plants and flowers ... and a lumberjack. You can use this giant tree with nearly every theme (it might be hard to use it with a space theme... )
This set has nearly 500 parts and is about 45 cm (18 inches) tall.