I enjoy constraining my (or others') OCs to the League of Legends format. I like doing this because it allows me to decide what is really important to a character's core values; and how they really act when pressured.
For example, Elphrihaim is the twin of fire and flames. He uses flames in combat, though exactly how was something I never finalized-- he could use soft flames to soothe pain and ills, or harsher flames to sear enemies, but most important was that he had complete-- free reign-- over his fire.
In my first draft of him, I represented that with an ult that allowed you to draw fire freely on Summoner's Rift.. which has a number of problems in and of itself; so I had to come up with other ways that would let the player create damage areas as they were needed.
The way I came up with that was with a simple point-target spell that was on an extremely short cooldown; having literally no effect if only cast once, demanding multiple rapid casts to deploy flame walls. That replaced his ult's 'free control of fire' gimmick, and was fit for a basic ability.
That let me shuffle around the single skill that felt ultimate-like (charged up ball of fire) to the ult, but I also incorporated his soft, soothing flames as a defensive buff that ended with a heal; that could be cast as a slow that ends with damage on enemies; representing the dual nature of his powers, to heal or harm.
Since I didn't want his unpredictable-location spell to have great range, I then gave his final spell pretty good range so that his back-line mage status wasn't shifted anywhere.
I do (currently) have him as a melee, but as he lacks mobility spells I'm probably going to make him ranged.
Other than that, I actually avoid skins because I usually prefer the 'Classic' skin of champions to their alternate costumes (exceptions I can think of: Varus (too dark), Jinx (outfit bugs me on multiple levels), Sona (because Silent Night is just a beautiful piece of music), Ahri (less dislike and more loving her skins), Trundle (trolls use mud not ice!), Caitlyn (Arctic Warfare's just too good), Cassiopeia (I am a Greek/Rome nut)).
Oh, and I suck at drawing but want to be a concept artist anyway, because I have ideas and lots of them.