Have you ever looked at ur base and said - wow,  this base sucks or maybe youve said Wow! my base looks great. but either way im going to tell some things you can add to your base and how to make them
-Brewing room- make a couple brewing stands (or buy them) and gather some materials (may require nether portal)

-Nether portal- great way of getting materials for the brewing room and a good way to farm off gold and also quarts for directions and may be a source of lava and netherack if you need it - can be made and here is a diagram of what to build

GOOG
O     O
O     O
O     O
GOOG
O = obsidian
G = gravel
Food source- this is basically a way to get food, this is essential but pretty easy, a great way to do this is to make farms, but if you have a rich faction you can use spawners or just buy food alone.
Enchantment room- this should be level 30 and is created using an enchant table and bookshelves here is a diagram on how to make this room
B2B2B2B2B2
B2             B2
B2      E     B2
B2             B2

B2 = 2 book shelves placed ontop of eachother
E = enchantment table

Automatic Cactus farm-Can be used for dye, but is very efficent to sell the cactus for money and become rich (perhaps you could start buying those spawners for food :D) also i cant really explain this one with a diagram :( so you should probally look it up. also remember - The bigger the better
Vault- a place for valuables simply make this room overprotected and add some chests and bam you got a vault

Public chest- a place where everybody can share their items through chests because remember, one mans trash is another mans treasure

Private rooms- a place to keep the players items they dont want to share or put in the vault\

Farms- make some farms pumpkin melon wheat netherwart by planting things and waiting for them to grow - great way of making food and getting potion materials


Well thats all i can think of for now so put in the comments if theres something i forgot because i probally missed a ton of stuff

PS: make sure your base is very protected with many layers of strong materials