Metal
Metal community, all subgenres welcome.
It only seemed fitting to have Lemmy himself as the icon.
Other Communities:
Dethklok's song was already suggested and it's the most obvious one and I'm pretty sure most metal heads would appreciate it. Straight up positivity isn't too common in metal outside of power metal. Even there it's either silly stuff or just more like anthems and shit. Not much about well wishes.
Closest thing to what you want that I can think of is Helloween's march of time. Sings about time passing and it has a positive message. I think it fits.
Something less obvious would be Mastodon's once more round the sun
Some other decent options that you can look into (or just make a playlist)
Serious black - older and wiser
Faith no More - the gentle art of making enemies
Gama bomb - 666teen
Andrew WK - party hard
We did think that "happy stuff" is power metal territory. Thanks for the suggestions!