My point is, it shouldn't be able be done twice. It should only done once, and awarded to users who reached something. Also, if you do the math, 75% of 100 is not equal to 75% of 200. So it should not be based on percentages because it wouldn't be equal for everyone, if that were to ever happen.
We're not considering custom Armatars at this time. But I do agree with you, there should be some sort of reward for gathering Quests. I wonder what else we could do?
Rather than giving users the ability to choose their own armatars, there could be a set of armatars that are only available to people who have a certain percentage of available quests. There could even be sets for 25%, 50%, and 75% to encourage people to earn more quests without feeling overwhelmed in the beginning.
They would remain unlocked once you reached that amount of quests, even if you stopped questing and the number of quests increased.