How much of a trill body is covered in feathers? Just the wing/head? All of their body? Does it vary from trill to trill? Is it hereditary? Is there a lot of variation in coloring? In feather length? In feather texture?
What are at the ends of their arms? Legs? Do they lay eggs? How do they care for their young? Do they have beaks? What is their family structure like? Social bonds?
What are common Trill personality tropes? Are they loyal? Obedient? Prone to bureaucracy (I mean, have you /seen/ hallifax? whose fault was that?)?
There isn't terribly much about Trillillial in the history or the lore wiki. And it's not clear how much mortals inherit from their elder ancestors after so many generations.
*cough* I may be getting a bit of a bug for drawing my character and
hallifax. More dumb and excessively detailed questions soon I bet.
Feel free to say "shut up and just art" too though.