First, there are some new icons sitting around the PBE folders.
|Icons for Morde, Anni, Shaco, and Yorick|
Secondly there is a new Summoner skill, called Barrier, that has been implemented for the upcomung ARAM Proving Grounds map.
As you can see in the picture above, it is indeed limited to custom games only and provides a temporary damage shield to your champion. Compared to heal, this is a trade off between Survivability ( short duration burst shield for when you know you are going to take hits ) and Sustainability ( heal gives permanent health back, but can be reduced by abilities, ignite, and other summoner heal debuffs ). According to RiotNome, one of the reds behind the project, "It's a new Summoner Spell for Proving Grounds that didn't make it to the PBE release. During development, it replaced Recall, but we since decided it best fit as a Summoner Spell."
Lastly, we have a few files from Jayce and the new olaf skin. The picture below, given to me by Skin Spotlights, shows Jayce's "wall sides" ( based on file names ), beside "Russian Knight" Olaf's axe model and, next to that, his shields for ult.