> coded image items compliant to the AVIF Baseline profile may not have a number of pixels greater than 8912896, a width greater than 8192 or a height greater than 4352.

https://aomediacodec.github.io/av1-avif/#profiles

I'm assuming if both the encoder and decoder support more than the baseline profile, then higher resolutions up to 64k x 64k are possible, although I would worry the file would be incompatible with some software.