How to make your house appear bigger
Keep your window to wall ratio high, even installing skylights or lightwells.
Install floor to ceiling bookshelves (and have a handy step-stool)
Use semi-opaque windows to let light into dark rooms.
Create outside space to make inside appear bigger.
Have fewer walls and more multi-purpose rooms.
Use the space under the stairs, in fact be creative with storage in general.
Replace doors with sliding doors.
Use glass to replace walls to trick the eye into thinking the rooms are larger than they are. Or use room dividers. .. or even curtains to divide rooms, as necessary.
Get creative with mirrors and reflective surfaces.
Shelves, shelves, shelves - in caravans they're all over the place!
Open storage draws the eye upwards, think in three dimensions.
Create the illusion of space by using low furniture.
Add colour - or even have a completely white room.
Keep lines and materials simple.
Carry flooring colour through from room to room to give visual continuity.
Think of your house in zones, demarcating each one.
Have multi-purpose furniture: can your sewing box double up as a stool when friends come round?
Have some see through furniture - perhaps a glass or perspex table.
Have fewer, but bigger, furnishings.
Customise - have furniture made to fit the tiny spaces available.
Don't display everything at once, ring the changes with the seasons.
Choose soft light colours
And lastly, CUT THE CLUTTER!