This game is a perfect execution of a concept that has very little going for it. If the mapmaker actually tries, it's trivially easy for the seeker to find it, with very little variety. And it's also easy to make a useless map and just remember where your own treasures are. Perhaps you could make it harder by randomizing where the seeker enters the map, or even put the map and island in different rotations so you have to orient yourself.
I agree with previous commenters that you should be able to see the stats for your submitted maps, with some kind of reward or ranking. Perhaps to encourage maps that are cryptic but still solvable, you could make it the mapmaker's objective not to have the seekers find the treasure quickly and easily, maps are scored based on how close they get to a 50% success rate or how long the seekers took.