A Dreamer's appearance can change pretty radically from their waking world self, to the point of being unrecognizable! This can include changes in height, hair and eye color, etc etc. Generally, though, they should still be recognizably human, though, if only for the practicality of being able to distinguish them for Torments. You can incorporate elements of animals/bugs/etc into their Dreamer designs (catboys real) but the base character should still be a human.