What is the function of the twenty-four thrones?

Revelation 4:4 (ESV)

4 Around the throne were twenty-four thrones, and seated on the thrones were twenty-four elders, clothed in white garments, with golden crowns on their heads.

In the eye of our mind we may picture twenty-four lesser thrones forming a semi-circle in front of God’s throne. That these twenty-four thrones are also called thrones indicates their importance. Yet they are important not of themselves but because they serve in proximity to God’s throne. Those seated on these thrones form (to say it in earthly terms) a sort of senate, a body of advisors. The fact that they are called “elders” supports that understanding. That there are twenty-four thrones, then, speaks to the greatness and majesty of him who sits on the principal throne.