The actual cosmetic should probably be related to bug catchers. Possible ideas for this cosmetic are a bug catcher straw hat for the hat slot, a bug catcher net worn on the head, a bug catcher net that goes on the back, or the gear for the Samurai from "Challenge of the Samurai". I personally vote the bug catcher straw hat or bug catcher net.
How this cosmetic is earned is up for debate, but I have a few ideas for this as well. I don't want the tracker to get clogged up with duplicate or invalid reports by players trying to get this cosmetic, so one of my ideas for how this cosmetic would be earned is that it is automatically given to players who had a non-duplicate bug ticket get marked as "Fix completed for upcoming version". It could also be automatically given to players who have created X amount of tickets on the bug tracker. It may also be awarded to players manually similar to how the Wiki Cap is awarded.