In art, antiquarianism refers to a person whose interest or devotion is things of the past.
In popular and positive usage, it denotes a person who has a passion and usually a wealth of knowledge of artefact from the ancient times. It may also be derogatory for any person who thinks everything must be great art and masterly crafted only because it happens to be from the hands of old masters.
The term is a tautology because the picture you photographed a moment ago is technically already belonging to the past, albeit the very recent past. So in the strictest sense of the word, we are all antiquarians.