OR/AS postgame

Nintendo and Game Freak put a lot of stuff in the postgame of OR/AS, I'm pretty sure I don't even need to mention the Delta Episode, but they added a bunch of little things that I found interesting/fun. Here's what I've found you can do after becoming the Champion of Hoenn.
Side note: this is under the assumption you've completed the Delta Episode already.

Hidden Kecleons
Remember when Steven gives you the Devon Scope on that bridge? This is required to enter Fortree City's gym. There are several other Kecleon hidden around Hoenn. There's one in...
-Mossdeep space Center. Behind the cutout of the astronaut
-Lavaridge Town. In the middle of the hot springs
-route 119. It's standing in front of the bike rails that are on top of the waterfall
-the hotel in Lilycove City. In behind the innkeeper and in front of the TV. Once you reveal it, you won't initiate a battle, instead you'll start some dialogue with the innkeeper that results in the Kecleon becoming the hotel's mascot.
These Kecleon will engage a battle with you upon discovery (with the exception of the Lillycove one) and as far as I know there's nothing special about these Kecleon. I may be wrong though.

The Gym Leaders and Elite Four
After beating the game, you'll see the gym leaders and elite four around Hoenn. You can't battle them, but there's some fun dialogue when you encounter them.
-Roxanne can be found in the house of that fossil maniac in Fallarbor Town.
-Drake of the Elite Four can be found on the deck of the S.S. Tidal
-Winona can be found on the roof of Mauville City, taking the place of a Taillow that was sitting on top of a tower. Funnily enough, the same Taillow can be seen on the ground, having its spot taken by Winona.
-Sidney of the Elite Four can be met upon entering the Battle Maison for the first time, apparently looking for Steven.
-Phoebe of the Elite Four can be seen on top of Mt. Pyre, off to the side. It seems she's talking to her deceased grandmother. Something I want to point out here is that the old woman who was one of the protectors of the Red and Blue Orb is gone.
-Flannery is seen in the Scorched Slab, apparently unable to catch the strong Pokémon that resides in the deepest part of the cave.
-Glacia of the Elite Four is mentioned by the two delinquents in the Mauville Food Court. Not sure if she shows up though.
-Liza and Tate are in the Lilycove Department Store, in the Decorations sections

The Battle Resort
Okay, I know everyone's disappointed by the Battle Frontier not returning, but there's still stuff to do here!
-a certain secret agent can be found here, and he gives you a mega stone
-two lovers from Team Aqua and Magma are here, and they'll give you a Camerupt and a Sharpedo
-after having 50 consecutive victories in the Battle Maison, Wally will be in the lobby to have a rematch against you. After beating him, he'll appear in the lobby randomly to battle you again.
-Multi-battles... just multi-battles. In this setting you go into a double battle with a partner, if you don't have a friend to battle with you can choose to battle with either Brendan/ May, Wally, Maxie/ Archie (depending on your version), and Steven. I have waaay too much fun with this mode.

And that's all I found. If I've missed anything, feel free to add on to this!

 

Welp, crap, you're right. I've dun goofed