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If Lazulis (Lapis) would be used for tools :3 that would be awesome

Flower Pot: Decorates your house with various plants on surfaces other than grass.
Inc Sack: Black wool, durr. Can also be used for Book and Quill, for multiplayer messages that take up too much space for signs.
Snow: Can be crafted to snow blocks, to create snow golems to help hold off monsters for you.
Dragon egg: A reward for killing the final boss, a good thing to show off.
Sponges:
In classic and indev, they erased 5x5x5 spaces of water, and from there
to 1.1 they also updated redstone in 5x5x5 spaces.
Cauldron: A more or less efficient way
to hold water. It may seem that you can also use infinite water sources,
but if there is no water around, it can accumulate rain in it. Also cleans dyed leather armor.
Lapis
Lazuli: A blue dye; can be used to make decorative lapis blocks that
can also be used as either decoration or a trap to make something look
water-ish.
Dead Bush/Shrub: With shears, you can pick them up and
place them as a good aesthetic look in flower pots or on sand in your
home or around it.

Cauldron: A nice looking way to hold water.Sponge: Used to hold, but now most texturepack artists use it as an extra block.
flower pot: Used to pretty up you house.
incsac: Well, squids need to drop something useful.
Dragon egg: A trophy showing you killed the enderdragon
snow: Well... biomes, snowballs, etc.
lapis: Blue dye, looks nice.
dead shrub: Fleshes out desert biomes.

But you are right, most of these are just aesthetics.

They are mostly for decoration.

Cauldron: Orginal way of brewing
Sponge: I think originaly it sucked up water
flower pot: I seriously have no idea...
incsac: well we gotta have black wool
Dragon egg: Thats just like a trophy for finishing the game
snow: well, they decided that you need biomes
lapis: Well.... Same as incsac
dead shrub: the desert would look boring without it
So yeah

Carpets however would be pretty cool. Mojang needs to remove all the useless crap, and add in more Aesthetic items like Carpets, and actual furniture. That way anyone can make their builds look cool (especially adventure map makers) instead of a fence + pressure pad serving as a table, and a stair being a chair.

+Dead bushes: THEY ARE SO BEAUTIFUL!