Have any prominent theologians written on what the ascension looked like?
Dr John Gill, Particular Baptist, commented that although it is not noted in either testament, Jesus' ascension must have been accompanied by "a shout, with the voice of the archangel & with the Trump of God" (1 Thess. 1:16) because He is said to return "in like manner" (Acts 1:11). Compare Psalm 47:5, Dr Gill's commentary: He having done his work on earth he came about, went up from earth to heaven in human nature, really, locally, and visibly, in the sight of his apostles, attended by angels, and with their shouts and acclamations, which are here meant; the Lord with the sound of the trumpet; which circumstance, though not related in the account of Christ's ascension in the New Testament, yet inasmuch as the angels say he shall descend in like manner as he ascended, and that it is certain he will descend with a shout, with the voice of the archangel, and the trump of God; so that if his ascent was as his descent will be, it must be then with a shout, and the sound of a trumpet, (Acts 1:10)
Similarly, Augustine of Hippo stated that, "He must return on a cloud as that is how He departed. To quote Augustine, "...And because there the angels even said, emphasized text He will come in the same way as you saw Him going into heaven, One should bellieve with good reason that He is not only going to come in the same body but also in a cloud, since He will come as He left, and a cloud supported Him when He went away." (Early Christian Voices in Texts, Traditions & Symbols, John Hermann & Annewies Van Den Hoek, pp.315, 316)
What we are informed about as to the appearance of the Ascension is that it occurred in a deliberately secluded location, Bethany (Luke 24: 50) having walked over the summit of the Mount of Olives a further 1 1/2 miles and 600 feet lower to Bethany, which was completely out of sight of Jerusalem. Further he was accompanied only by His closest 11 disciples (Judas being dead & Matthias not yet chosen) & only whilst He was disappearing was their wonderment & reverie interrupted by the "two men in white" (Acts 1:10,11) whom some commentators believe to be Heaven's witnesses, Moses & Elijah (cf. Rev.11:3; Zech.4:14; Matt.17:3;Luke 24:4)
Hence we may glean something of what the Ascension looked like, notwithstanding the comments of Gill & Augustine. As with Christ's Post-Resurrection/Pre-Ascension ministry it was a very private affair without fanfare & restricted solely to believers. And we are informed that Jesus will return or "shall so come in like manner" (Acts 1:11).