Over the last few days I have been adding a few new boons to the post I made last week*. 12 for dragon sorcerers, 4 for wood elves, 1 for tieflings and 1 for all spell casters. And I plan on writing more as the ideas come to mind. (Edit, I added 15 more for  backgrounds. Edit 2- added 20 more background boons. Edit 3- 10 more in the new category Powerful Boons.)

The thing is as fun as designing new epic boons is, I think that a predetermined list is limiting in some ways. The boons should be customized to the character’s class, race, personality, and especially deeds (as boons do not appear out of nowhere, one has to earn them). Of course it is impossible for any author to create such specific boons, so all I can do is provide suggestions, ideas for you to take and modify to your needs. Which is why boons, both the official ones and my own, are unbalanced against each other. The power level of different home games makes it impossible to codify them to the point where they would be balanced and I think that is a good thing.

* http://d-infinity.net/game-content/new-epic-boons-dungeons-dragons-5th-edition