In the past it has generally been mounts such as Twilight Drake, Black Drake, Blue Drake, Blue Protodrake, Green Protodrake, etc. They will probably also add the drake from Cata out of Stonecore. However I don't think things like Invincible, Mimiron's, Time Lost, the mount from Deepholme, and probably the Elagon mount will have a chance to drop. As well as the ones from DS and FL.
I was meaning that it is like the bag from being a tank. It is not loot specific to the boss, but instead just an overall chance of something to drop. Also, not to shatter your hopes but the mounts have somewhere in the area of .01% chance to drop.
I would guess it is the same mounts as from the satchel. It seems those are the less exclusive mounts that they are willing to hand out to a larger group of people for minimal work. Doubt it will contain things like ashes or invincible.
The bags gained via LFR now have a chance to contain bonus rewards, including consumables, Spirit of Harmony, rare pets or mounts, and greens and blues that drop in normal and heroic mode.
so.... does this means that if you do Elegon in LFR and get the bag or loot or use coin, you have a small chance to get the mount as well?
I'd assume the satchel functions exactly like the Call To Arms satchel in terms of what can be looted.
100% random gold
100% some non-gold item. This includes stuff like minipets, gems, flasks, potions and certain mounts. I am not completely familiar with what mounts can be found in the MoP satchel but the Cata satchel only had dungeon mounts from Pre-Cata dungeons. No raid mounts could be looted from the satchel.