[mikepurvis]

Earth is 12700 km in diameter, so such an image would be 688 pixels across.

Basically you won't be reading license plates but you'd see enough to identify evidence of very large scale construction, and with multiple images over time I bet you could draw even more conclusions.

[escapecharacter]

We could make a license plate big enough that aliens could see it and know we are sophisticated.

[prerok]

Nah, let's just put a big sign "Kilroy was here", so they don't bother with the "mostly harmless" planet.

[kazinator]

If four out of seven digits were blurred out, then they would really see how sophisticated we are: we have the concept of privacy!