wooden floors

kitchen cabinets

put stuff near where you use it!

bathrooms

Build drawers in the wasted space between studs in the wall.

home theater/stage

amazing family-sized home theater with star-gazing moon roof and big leather sofas!

I really like the walls on this one!   Notice the stage up front.  (don't need a star-gazing roof...)

innovations

These useful, discreet vacuum baseboards

The tiny slot sucks up dirt that is swept nearby, then stores for easy disposal.

Useful hidden storage areas beneath the guest room

This sneaky refrigerator under your kitchen island. (minus the beer)

finishing touches

There should be a back stairway close to the kitchen that has a huge tube slide leading from the upstairs bedrooms to the downstairs (kitchen) so the kids can slide down for breakfast.  I like the spiral slide on the left - no tube required!

Near the garage should be a boot room with lockers for the kids to put their coats and stuff.  (Doors, a bench, hooks, and a place for shoes.)
A drinking fountain near the boot room is also a good idea.

the bedrooms

One thing I took from the Perot house in California was the idea of having a room for each child - even after they had left home to have families of their own.  To be self-sufficient, each room had a fireplace (a working wood one since they lived in a forest and could heat each room if need be.)  Each room also had a bathroom attached and a queen sized bed.  There was plenty of space for kids to lay down sleeping bags, etc. as each room was the size of a master bedroom suite.
Not saying we could afford all that, but the idea has merit.