"A lot of things we buy, or rather the particular type reflect status markers - a Suzuki Swift might get you to work, but a Lamborghini Diablo is a statement about how you want to be seen, and that is 'wealthy'. Therefore a fashionably decorated, expensive tree is a marker that one may wish to be seen as sophisticated and high status.
"A poorly decorated tree might signal you don't give a toss about how you're seen, or that there is another reason - like nostalgia or tradition."
Real or artificial:
"One thing consumer psychologists (and personality psychologists) would go to pains to point out is that our consumption decisions say something about our psychology, but also our circumstances. For example, people who are vegetarian score higher on the personality trait of 'Openness to new experience' but that doesn't mean that all university students who don't eat meat are high on openness - they might just be too poor to afford meat! Same applies to trees - a good artificial tree is expensive, and you can get ripped off too for a real one.
"I can fairly confidently say that a real tree means you probably don't have allergies."
White lights or multi-coloured lights:
"Monochromatic or single-colour schemes may indicate lower openness to experience and agreeableness, particularly if they are non-fashionable colours - you non-conformists you."
Traditional or hipster?
"A trendy tree is more likely to be a status marker. Higher on impression management (or social desirability bias) - you care how people see you. Traditional reflects more deference to authority and tradition."
Perfectly symmetrical tree:
"Low on openness and high on conscientiousness, high on OCD!"
White, silver or gold trees as opposed to the traditional green:
"There's no guidance in the research, but theory would suggest gold and silver reflect greater endorsement of values such as power and social status, while green means equality, benevolence."
The anti-tree - simply decorating a plant that is already in the house:
"A half-hearted attempt. Okay, again openness to experience (goes with non-conformity) and low on impression management - you care less about how you are seen by others."
No tree at all:
"These types can be introverted and are low on being agreeable. Or poor. Having no tree may also signal anomie - the feeling of not being a part of a community or social group."