Haha, I was gonna try exactly that, but I got too lazy trying to install pypy3 on my shitty centos box. My other option was to translate it into real assembly, but that also seemed like more work that I wanted to put into it.
I wrote a compiler from emoji-code to amd64 (mostly because I'm more interested in compilers than reversing). It runs quite fast - prints the whole domain in ~1 min. I'd highly recommend it to people who are into assembly, it was a fun exercise.
Was your method fast enough to get all three parts of the URL?
I'm guessing the flag may be in the rest of the message to be decoded.
I scrapped and downloaded around 55 pngs.
As the comment above implies, it seems like my approach was wrong and the answer is in one of the images I guess