Velber
I find myself thinking about this again
The mural depicts the three Velber siblings, and Velber itself, the large creature with the single eye Sefar is there, and there's some sort of elder man there too, who I assume is 01 aka the “Older Brother”. So does that mean that 03 the “Younger Sister” is the flowers at the bottom? Extella did say the three are drastically different from each other since they are based off of different lifeforms from different planets. Furthermore, all three were apparently sent to earth if I am correct, so 01 and 03 could be just about anywhere right now. Makes me even more intrigued since 01 could also be a Heroic Spirit going off his appearance. I hope we learn more about 01 and 03 someday because the lack of info on these two kills me.