In case this is the first time you've heard of a texture update, IronStylus described them as:
"The texture updates are really a result of our dedicated 3D artists taking some time to give champions who don't need an overhaul some love. You'll most likely see more of these sneaking in here and there. We don't want to make too much of a big deal because they're more like us doing polish work and cleaning house rather than doing something that needs big fanfare like a complete VU"
3150 IP or 790 RP
Not available - Legacy Skin
Not available - Closed Beta Tester Reward