Gardening or fishing pet drops may sound fun! Here is a couple ideas to start off with...
Gardening drops Tanglewood Vine (to go along with the mount) School: Life Dropped by: Angel Oak May Cast: Fairy friend and Mend Cards: Satyr and Rebirth
Seedling Sprout Dropped by: Dandelion School: Life May Cast: +40% Lifeblade and Unicorn Cards: Dryad and Mend
Fishing drops Lil Chest Found in Treasure Chests across the Spiral School: Balance May Cast: Balance-spear and Fairy Friend Cards: Punishment and Chastisement (2)
Lil Sharky Found by looting Treasure Chests in Celestia School: Storm May Cast: +35% Storm-blade and Galvanic Field Cards: Tempest and Storm Lord
Starphish Found by fishing for Little Mackerel in the District of the Stars in Celestia School: Star (might be the first of it's kind!) May Cast: -25% Fortify or +25% Amplify (seasonal) Cards: Infallible and Vengeance
I may not be entirely elaborate on the style of the drops. It is just and idea after all.
(might be the first of it's kind!)