Build a trash(-block) heap. If you just wish to fill it in with something that looks interesting, then just fill 'er up with a random scattering of all the blocks you consider to be worthless, common, ugly, useless, or pointless to have in bulk. When you get it filled up most of the way to where you want, start laying down definite mounds of each block. Once you have the mounds completed, decorate the mounds with random stuff that you might find in a trash heap...discarded machinery (furnaces, workstations, crafting tables, etc), bits of old circuitry (redstone stuff), a hardy flower or two busily struggling to survive a harsh environment, maybe a puddle of water, etc.
You could incorporate an incinerator in this by burying some strategically-placed hoppers throughout the heap that then send the picked-up items to a buffer. The buffer would be your last-chance storage to pull something out so that mistakes aren't so immediately permanent, so you'll want to have a really big buffer to avoid major backlogs throughout your hopper chains (nothing's worse than accidentally throwing your god sword into the trash and then not being able to retrieve it because it's stuck in some random buried hopper you don't exactly recall where it is). You could encapsulate this buffer in a nearby incinerator building that has an industrial "furnace" for destroying trash.
If you instead wanted some "junk storage", you could use those strategically-placed hoppers to catch items you toss onto the heap, either storing them at that spot or bringing it all to a hidden sorted storage system.
You could even combine the trio of concepts so that your trash heap is your main storage input (just throw items you don't want to hold anymore on the ground, they get picked up and sent through a sorting system to "recycle" the valuables, and anything left unsorted gets sent off to be incinerated). Combined with some timing circuits, you could have your various processing buildings only operating at specific times of the day to suggest there are actually workers hard at work there. You could perhaps even incorporate an unofficial "grey market" by utilizing villagers as your workforce, their trades being small bits of junk they've kept for themselves.