Table image may be built up in different ways depending on the type of play (live or online).
The question was about online.
In online games as in live games one part of your table image comes from the runouts/showdowns players see from you.
Another part of your table image comes from stats if HUD are allowed or are implemented by the
poker site.
The stats give only a very rough overview if the sample size is very small,
but can give hints if a player is more thight or loose,
and the aggression is also relatively good shown (non poker room stats).
Depending on these factors, a table image of a player can be built.
Most players will rely on table images like maniac, nit, passive or aggressive player
and try to adapt their playing style according to that table image.
So I think it is important.
But what is also important is to mask your table image, so that the adaption is a bit more tricky.