Rev 16:13 And I saw three un-clean inspired expressions that looked like frogs come out of the mouth of the dragon and wild beast ...14 They are, in fact, expressions inspired by demons and [they] perform signs, and go forth to the kings of the entire inhabited earth, to gather them together to the war of the great day of God the Almighty.
If I may, I'll suggest one answer, maybe you have another?
Spirits are invisible and intangible; hence the "unclean spirits like frogs" symbolize propaganda, proclamations and messages rather than tangible things.
A frog is a kind of animal that has a big mouth, assumes much wisdom, looks wise, bluffs a great deal, swells up and makes much noise.
Notice that Revelation has three unclean spirits like frogs. Could this signify a trio of declarations, principles and proclamations ? All of these are from God's point of view: boastful, arrogant and claim much.
If we are to assume that the "Dragon" is Satan and his spiritual organization,
and the beast the visible part of his organization made up of the commercial, political and ecclesiastical factors.
This could be an example of such claims:
One:
God is a liar and his word is unreliable, contradictory and unpractical, ignore him, and those who advocate his cause.
Two:
We have the only established form of government and guardian of religious truth that is proper,we will make the earth into a fit place to live.
Three:
Our wealth, power and science is our god, not Jehovah. We are the spiritual guardians for the people, nothing else should be heard or considered.
Can you hear the frogs? What do you think they mean ?