Normal clutter may or may not have a specific theme.
The items are not acquired in a planned fashion and are not excessive.
The clutter is disorganized but generally localized in storage spaces. It may also intrude into living spaces but it does not prevent one from using the space as intended.
The thought of getting rid of the items not acquiring more does not cause distress. The clutter may cause mild distress but does not have any lasting impact on one's life.
Source: 5th edition of the Diagnostic and Statistical Manual of Mental Disorders (APA, 2014)