I made these for the game token contest.  Cap's shield and Mjolnir I made from scratch in tinkercad, but Iron Man's helmet and Hulk's fist I found on thingiverse and scaled down.  Here's the originals https://www.thingiverse.com/thing:360747 and https://www.thingiverse.com/thing:3646021.  I wasn't sure how else to credit those two.