Last year it was like lemmy's version of reddit's r/place, but cooler. It's happening again this year, not sure if there will be any changes to it other than there will be less pixels this time.
There should be a website up then. It's in like a month. More info can be found probably at !canvas@toast.ooo. There's also a matrix group which is how I found out (I don't know the link sorry)