Although this is not much on gameplay, it is rather something to save us from boredom. Although I like MMO's, I usually get extremely bored after questing in the same area over and over again. I want TESO to fix this. What'd like is more;
Varied enviorments, but not unrealistic.
Aquatic mounts and questing in new aquatic areas.
No flying mounts. (Does those even exist in TES lore?)
Mounts that can only be used in special enviorments.
Mounts can be summoned by using a horn which will make it spawn 30 metres away and run up to you, so it feels like it doesn't appear out of nowhere. When you jump of your mount, it will stay at the same place until you choose to remove it or equip it again.
Two separate bags for where you keep your loot. One bag which cannot be taken by other players if you die which has about 16 spaces. Players cannot take your gear. One bag which has about 24 spaces where players can steal your items from. This way, PvP will be more dangerous but also rewarding.
Some new areas and island that we haven't visited or aren't on the map, but not too many. That would ruin the feel of the game.
And of course, a lot of easter eggs. I love easter eggs.