The size of the room, as well as the natural light in it, will definitely be a deciding factor when choosing the colour of the tiles. 

Borders will decide whether the room is to appear classic, modern or rustic.  In shower/bathrooms, borders can be laid vertical, horizontal or a combination of both. 

You can also find whole decorated tiles that are used to create either complete feature walls or to enhance sections of a particular wall. 

Smaller rooms will benefit if the tile chosen is rectangular and is laid horizontally.  It will make the room look larger.  But then – each room is unique and should be treated as such.