I can’t get it to decode, even after correcting the base64 padding. Firefox just shows the broken image icon. My image viewer throws out the glorious log message Image format is actually "png" not "png", along with a bunch of checksum errors.

I guess, the checksum can’t be correct when it’s cut off, but none of my image viewing/editing software wants to look past that.

In a hex viewer, it looks like this:

Compared to a normal PNG:

I don’t know the PNG spec by heart, but I guess, it doesn’t look completely off the rails before it goes there…