Usually, when a family buys a new house, space is not a problem. For this reason, the attic is left unattended, and is used for storing stuff or not used at all. It gets dusty, with spiderwebs and useless things.
But one of a sudden, either the family grows (just because a new member comes in or because two brothers or sisters sharing a room want one for each of them), or new needs appear (you realize that an additional bathroom would fit conveniently, or need a space for working at home, or just a family room where your teenage kids can share with their friends without disturbing your peace). There you have the attic!
The first problem you may face, though, is that the attic may require some remodelling or, more properly, needs to be finished. You will probably have to paint it, or cover the floor with appropriate material (in this case, parquet would be a convenient option, see our post regarding parquet) and, in the worst scenario, make electrical installations (and, should you want to install a bathroom, plumbing and bath appliances).
If you do not want to invest to much, you can still give the attic a rustic touch, using wooden beans on the ceiling, or, by leaving some electrical or plumbing installations visible, you could give the space some modern touch, too). Once you have done this, keep in mind that the attic is usually not to high, so it is better to use colors (like white), that gives some sensation of space, as well as some mirrors on the walls, for instance.