Some of these things are just pointlessly rude, not even dark. I mean, "fart on a dream character"? I thought the point of the option of dark lucid tasks was to make things interesting. If all you're going to do is be mean to DCs, there won't be any point to it.

More suggestions include:
-focus on the darker side of shapeshifting (pain? grotesqueness? all the details you never bother with in a lighter dream. Also holds for regeneration of flesh, if a death fails)
-compare different ways of dying (drowning, burning nitrous oxide, systemic organ failure)
-test dark magic spells
-break a DC in under eight hours, real time
-contact dark and malevolent creatures, and release them from your control as the dream creator.