Custom hats
You can now use a very beta and unstable feature, which is the birb hat workshop. You can create your custom hats in the Hat Editor in game (accessible in the main menu) and upload it to Steam Workshop, where other people can subscribe to the hats they might like and then wear them in the game.
For multiplayer matches, if you choose to wear workshop hats they can be automatically synchronized if other players have enabled a setting to allow these downloads.
(there's a type in the setting name)
This feature is still quite early in development even though it took a long time, so it's not yet translated and the editor is thus only available in english. If you have any problems regarding this new feature, or any other feature you can start a thread on the community page.
(Very simple hat editor)
Small patches
Fixed tab switching in the lobby to react to both keyboard and controller
Be your best birb self achievement should now be achievable every time you beat your personal best on any map.
I am also working on a native linux build, so you may expect that in a near future.