I love thinking up of skin ideas for champions I randomly get in an ARAM. This is what I had:
Model: Leona's armour is completely made out of mud and wood, with her head adorned with a halo of twigs to make a wreath sitting on her head. She wields a sword, roughly hewn out of stone and mud as well. Inscribed on the blade are earthern runes that glow between a green and brown. Instead of a shield, her hand emanates a constant green pulsing that shows her using magic. Attacked to the same forearm magically, she has a boulder that floats in place.
*Sunlight:* Leona's abilities mark enemies. The marks creates stone shackles around the limbs of the target. When hit by an ally, the stone shatters, dealing damage to the enemy.
*Shield of Daybreak:* Leona closes her fist in front of the target, summoning roots to burst from the ground and lock then enemy in place as it stuns them.
*Eclipse:* Leona gathers boulders, rocks, dirt, and other debris to swirl around her in a whirlwind. After a couple of seconds, Leona repels the debris outwards to damage all enemies. The stone attaches to Leona's armour, increasing her physical stats and changing her armour model to stone for a short time.
*Zenith Blade:* Leona uses her shield-using and spellcasting hand to summon roots from her hand that travel in a line. The last enemy hit becomes rooted as Leona pulls herself to them.
*Solar Flare:* Leona throws her stone at a target location. When the stone strikes the earth, a earthquake radiates out from it, dealing damage and slowing enemies. Enemies directly hit by the boulder are stunned. Leona's sword becomes a glowing mass of green, earthen energy for the next few attacks.