What makes up a Huskylens 'tag'?

The Huskylens tag recognition feature works great with the sample tags in the tutorial. Is it possible to make my own tags, different from these? It looks like the tags are all 8x8 blocks with a black border. Is that a fixed design, or could I make 16x16 tags, for instance? Do the tags need a certain percentage of black and white squares? What are the rules for what constitutes a 'tag'?

Thanks for any word on this.