Okay, I think I’ve found another function that nobody knew before.
Arraytype 63 is just like arraytype 61 (described before) except that you add another picture (has to be the last one) that will be shown if the watch is charging. So, you can add between 2 and 100 pictures for the battery status (the last one of those being for the fully charged battery), and then another one after the last one for when the watch is charging.
If I recall correctly, before the only battery symbol that was allowed was the one by default.
Hope this is useful!