An interesting thread this, Jaiotu. I'd come round to the idea that the message in the UP was the message, and there isn't anything else. The binary is so obviously binary, and the spectrograph is blatant enough, the question is the resolving of the pictograms. If you wanted to communicate an idea but you've no shared language, no point of context or reference and 640x640 pixels to do it in, how would you do it?
Most symbology is human or earth centric. How would you say 'we come in peace' without a central reference point? Our only shared knowledge would be maths and physics, possibly music, space travel, chemical reactions - universal tropes.