Consider having very light and non-structural partitions between rooms. If you are designing the house from scratch a difference in levels can do the needful gracefully. Could be utilitarian yet engraved. Arrange all objects in the room along the walls. This gives an illusion of more space.
Shapes Try to have a similarity among shapes of the objects in a room.
Angular furniture should be complemented by accentuated angular wall hangings, lamp shades and other objects. This, however should not be taken too far, and may result in monotony. Colours Frequent change of colour combinations in the house will prove to be effective, and a challenge to one who is doing it as well. This will not turn out to be costly, if one takes less expensive, and effective elements for the colour changes. The wall colour, which would be rather permanent, needs to be given a neutral colour that will go together with shades of reds and blues.