Were standing (ιστηκεισαν). Past perfect active of ιστημ intransitive and used like an imperfect as in Joh 19:25.

R…

And all the angels stood round about the throne. (See Barnes on Revelation 5:11).

And all the angels... — Translate, And all the angels were standing around the throne, and the elders, and the four living bei…

After this I beheld, and, lo, a great multitude, which no man could number, of all nations, and kindreds, and people, and tongues, stood before…

And all the angels stood round about the throne
The holy and elect angels, even all of them, the ten thousand times …

The first fruits of Christ having led the way, the Gentiles converted later follow, and ascribe their salvation to God and the Redeemer with triump…