In my current survival world I'm trying to incorporate all my main buildings into my main base instead of spreading them out throughout the biome. So far I've just got a main area with a mostly decorative kitchen and living room (kitchen includes furnace, cauldron, and some chests, living room just has a crafting table), a crop and small tree farm, an animal farm, an enchanting room, and a bedroom. Further down the line I will put a brewing stand somewhere and maybe some related accessories. Possibly a darkroom mob spawner too, or find a way of hooking up a cage spawner I found deep underground. But other than this I'm getting a mental block on ideas. So ideas and suggestions would be really appreciated - please and thank you!
A trophy room - display records, the dragon egg and any other really rare items you get in the most extravagant way you can think of
A room for clothes and armor, using armor stands - Since leather can be dyed more than once, the color combinations are endless! You can also make different sets of enchanted for different purposes: diving, fighting, jumping etc.
A Collector's/Souvenir room or similar for different biomes - It could be made as a museum, exposition or garden. I could be done in tandem with the exploration achievement.
A storage room for TNT and fireworks. Build it super-safe in obsidian or some other equally blast resistant material.
Build a TNT-cannon on a roof or a tower if you have one. Then blow up a mountain next to your base X)
Redstone automation - Automated smelters and sorters are a good brain challenge!
Some interesting redstone door to get in and out of the base.
Almost everything i would have said has been said. Except i would make a colored wool factory, a working casino, hidden potion shop, water ways for boat travel ( as an alternatove route to minecarts), armory with a suit of armor for every adventure so an overworld suit a mining suit a nether suit an end suit and whatever else but every armor is fitted with enchantments necessary so mining armor would have blast protection for creepers and depth strider for water. I would make a slime farm. I love making mueseums for artifacts from adventures. You could build a wall if you dont have one. a cool way to open the doors to the wall. a walkway around the wall. have an elytra launcher so make a tower and ontop make a slime launcher to shoot you up in the air. You could build watch tower. Build a moat around your wall. Make a steak grinder. Make an armor fitting station in your armory. Make a mock nether on the overworld for your portal. Trick out your kitchen. Make a banner or firework creating station.