Meanings of abstract object in English

Flat white setting, combining Brecht and Oriental theatre against which ponderous abstract objects dangle.

Abstract objects cannot be placed inside physical devices; with computers one can only represent text and act upon those representations.

Not only were the graphics completely inscrutable -can you even tell which of these abstract objects is supposed to be Indiana Jones?

Most of these are pre-Columbian, but some of the chalices and carvings have a medieval European look, and there are certain abstract objects (of ivory?