I am not an expert in Wittgenstein but I did study Tractatus and Philosophical Investigations in undergrad.

Perhaps this might help. At 2.202 he states that “A picture represents a possible situation in logical-space.” Here he introduces “logical” pictures as representations of the world. Pictures for Wittgeinstein act as representations insofar as they represent possibilities which are inherent in the world. In other words, they represent either existing or non-existing facts about the world. These facts are supposedly properties of an object that are so simple, they cannot be further reduced.

Thus, an object is simple insofar as it cannot be analyzed as a complex of other objects (but they must exist or it would be impossible for us to picture the world).