I kind of agree with a bit of what has been said regarding only drawing tasks. I have no issue with one or two drawing tasks though as long as there are other options for those that are artistically challenged.
Trials for me has always been a balance between PvP and non-PvP, so having multiple ways and outlets to showcase your knowledge and devotion to an element would be best.
Here are a few suggestions of various tasks:
Drawing task(redraw a card art for a card in your element, (re)draw art for a card in
crucible/
forge/
armory that is in your element, draw a new element symbol for your element).
Writing Task(a guide explaining various positive and negative synergies with you element, a story about your elemental realm making sure to include at least X cards from your element in your story, a news cast play by play of a previous trials final match in your element)
Cardbuilding( design a new card for your element that fulfills a currently missing role in your element, design a card in another element that uses your element as an active ability or synergizes with your element)
Deckbuilding(build a mono duo and trio with your element each fulfilling a different deck archetype, design a new tournament and build X decks for it that favor your element, build a set of decks that could counter a previous final battle or set of war matches and explain why they were chosen, build a set of decks for war based on a given starting vault)
Extra Phase 2 PvP(usually having the option for a few extra PvP games is popular.)