Okay, this is probably not a day. companies don't operate 24 hours a day. It's 8.
If Riot is like any other development company, it'll go like this.
- Designer has to come up with a new facial expression for Sej.
- The person/persons potentially have redo the drawings from scratch around her head and redo light shading and coloring.
- They have to send it to someone who may or may not approve the new design. If not they have to redo everything.
- Once approved, a developer has actually to put the assets into the game.
- QA has to test that they didn't miss or mess up anything.
- The patch is released.
So if you think that'll take 8 hours within a work day where you have meetings and other projects then you probably haven't worked at a software company before. Also whose gonna pay for that. They could be working on skins or champions with that time which would earn a lot more money that fixing a skin for a small group who own the skin and the even smaller group who want the splash changed.