I thought I would include some of what the Baker Exegetical Greek Commentary on Revelation (Grant R. Osborne, p.229) has for reasoning that the 24 elders of Revelation were/are angelic in origin:
[After listing the various views that think they are human in origin, not all for the same reason . . .]
However, many others ([various comemntators listed]) believe these are angelic figures. There are no other human beings in [Rev] chapter 4, and in Isa 24:23 angels might be called "elders: (it is debated whether they are angels or the elders of Israel). In Ps 89:7 (cf. 1 Kings 22:19; Job 15:8) God sits in the "council of his holy ones" (=angels). Moreover, angels are called "thrones or powers or rulers or authorities" in Col. 1:16 (cf. Eph 3:10; 6:12), and they wear white in Matt. 28:3; John 20:12; Acts 1:10. [Bobcat - This last argument counters the argument that they must be human because of wearing white.) The thrones and golden crowns could refer to their royal function under God similar to the way first-century kings were subject to the Roman emperor.
The key is the function of the presbyteroi (elders) in the book [of Revelation]. Their primary role is that of worship (5:14; 11:16; 19:4) and praise (4:11; 5:9-10; 11:17-18; 14:3; 19:4). In addition, they serve as intermediaries and interpreters (5:5; 7:13-17). A close examination of these texts shows a distinct differentiation between the elders and the saints. In 5:8 they hold golden bowls that contain the prayers of the saints; in 7:13-14 one of them explains who the victorious saints are; in 11:18 they thank God for rewarding the saints; in 14:3 the 144,000 sing "a new song before the throne and before the four living creatures and the elders"; and in 19:4 they join the heavenly chorus. The elders are seated on thrones (4:4; 11:16), while the saints stand before the thone (7:9). From this evidence it is more likely that these are heavenly beings who reign with God and are part of the retinue surrounding his throne. Moreover, since "all the angels" also stand before the throne (7:11), these must be celestial beings with a ruling function. [Bobcat - Thus, Daniel 10:13, "one of the foremost princes" which included the angelic Michael, with the phrase being spoken by an angelic messenger.]
[End of quote. Material in square brackets was inserted by Bobcat to fill out the context]