>I think in general dumping in ones own thread to make it active isnt such a bad thing either?
Of course not - providing images is the whole purpose of an imageboard!

The things that are generally frowned upon (on imageboards historically, and not just Heyuri) are:
- dumping things that go against the topic/spirit of the board
- making self-serving demands/requests telling other users to provide you with material (especially without offering anything desirable in return)
- creating threads with overly broad topics (i.e. "funny pics" thread on a board that is largely about posting funny pics)