So when i first started playing ESO back in the beta, I enjoyed trying to find buried treasure after I found a map. It was neat and I felt like I accomplished something when I found it, until I opened it up. The loot was bleh, and it turned me off from wanting to search for more. Now I just try to give the maps away, and destroy them if no one wants them. This is a fun part of the game, that is not very rewarding.
When I first got a treasure map, my mind immediately thought of a MMO i played years ago, Runescape. In Runescape, when you found a treasure map, it would give a clue in the form of a picture (much like ESO), a written riddle, or Coordinates (you actually had to use a sextent and a few other tools to find your coordinates). Once you found the spot the clue led you to, you would usually get another clue to a different locale. After a few clues (somtimes up to 10), you would get your loot. It was alot of fun and the more clues you get the more excited you were to get your chest. After a while, you could just search the locations online, but the reward was worth it.
now thats all fine and dandy but in ESO, the reward isnt worth spending an afternoon going from clue to clue to get 40 gold, a blue item, and maybe a soul gem. Runescape's chests would contain costume peices, rare mats, valuable stuff to sell, and sometimes very good weapons. A grand majority of the rarer things, could only be found by opening those chests. The reward was great on many accounts.
I dont expect ZOS to go the same route, i was just giving an example. As it stands now, Treasure maps are just some junk taking up inventory slots. It would be nice to see them turn into something fun and rewarding for the players invested time. I could also say the same thing for fishing as well, but I think that topic has been covered by many others already.
Its something to consider ZOS. If you gave one of your maps to Nathan Drake, he would blow his nose in it and throw it behind him.