There's your Rival in Kiloude City. They can be battled once per day. The trainers in the Battle Chateau will also reappear. You can also re-face gym leaders in battle Chateau.
Do the restaurants count? If so then Le Wow and the rest of them in Lumiose City can be challenged.
There is also the Battle Maison.
I think that's it, but since this is just off the top of my head I might have missed someone...