It depends on the function. If I would have a ship designed for combat, prepare for a very clean, straight and metallic design. A lot of places that lead right to the hangar, the barracks, cantina and armory would be very close to each other. The only place that would not be as accesible as the rest would be the bridge.
For an non-combat ship, I would make it very uhh, fluffy
Red carpets, red couches, red curtains, wooden doors. I am thinking of a ship about twice the size of the millenium falcon from star wars.
By the way, if you like to design the interior of your ship, you should really give star wars galaxies a go
Ships are cheap (well, the less usefull ones are) and the furniture can be bought from player shops. They however, are, compared to the ship, pretty expensive 
You could also create your own furniture (note: You don't actually design it, but rather choose the colors and blueprint) and ships.