Decor changes reflects a changing of colour, size, shape or tone in a space or room. Making it more pleasant hopefully.
Adding or taking away a screen, cushions, mattress cover or rug is an example of a decor change.
Especially relevant would be introducing a Room Divider or a removable futon mattress cover. A dominant 4 panel Screen, something that can partition a room is probably the easiest example.
But while a room divider introduces a change to space a coloured futon mattress cover can change the mood of a room. As seasons change so colour through cushions or a rug will augment that changing seasonal feel.
In addition a dominant piece should contrast to other elements almost like an opposite attracting sort of thing.
As a result of these contrasts and changes of larger pieces so smaller changes will be most noteworthy. A set of prints or maybe a vase of flowers as a result make a statement.