[lowbart]

Hmm... the icons would be more distinctive if they were bigger, yeah.

How about:
"We admire your recent advances."
"Now is not the time for alliances."
"This trade is mutually beneficial for our peoples."
"Your cities shall burn with our vengeful fire!"
"We have revised your trade proposal. It is now acceptable to us."
"We look forward to your future offerings."
"Your empire is about to fall, we demand your surrender."
"You have fought valiantly, but genocide is not what we desire."
"Your military prowess is exceptional."
"We welcome our new ally. You have made the right choice, [%TargetEmperorTitle] [%TargetEmperorName]."
"Do you expect to lay claim to the entire galaxy?"
"We will not support such a reckless endeavor."


Actually, the Mega Evil Empire ones might be the best (and most easily recognizable:

"Your vile race has spread beyond any natural limits. We shall destroy you before you consume us.

"We can no longer let you take over every planet in sight. You must be stopped."

"Your civilization has become a threat to the rest of the galaxy. We cannot allow you to continue."

"The rampant expansion of the [%TargetEmpireName] cannot go unchecked. You endanger the other sentient races."

"The [%OurEmpireName] cannot allow you, [%TargetEmperorTitle] [%TargetEmperorName], to threaten us with your massive empire. Your very size makes you an intolerable threat."