Two aspects of Paul's sermon might seem to imply a broad concept of revelation. The first is his use of the Athenian's 'unknown god'. Of course, in and of itself this is nothing more than an incidental point of Athenian culture, which was crowded (physically and metaphysically) with gods. However, Paul states his intention in his sermon thus: "what therefore you worship as unknown, this I proclaim to you". Is Paul here identifying the God of the OT, and the Father of Jesus Christ, with the Athenian idol? Is he saying that the worship the Athenians have directed to this unknown God has in fact been directed to the Creator God?
In my opinion, the answer to both questions must be 'no'. I'll come to the reasoning behind this shortly. But first, notice that the whole point here is that the Athenians do not know God. The altar to the unknown god represented, for them, the simple enough pagan fear that they might have overlooked a deity. For Paul, I would suggest, it represents more profoundly the emptiness that lies at the heart of all pagan religion. The fact that the altar is there testifies to a space - a void - that exists within this religious system. That void must necessarily exist in any religion of untrue gods, for religion is directed toward a deity (or deities), and unless the direction is toward the true and living God all the worship, prayer and devotion simply disappears into nothingness.
The second point which might seem to indicate a broad concept of revelation is Paul's outline of history: "he made from one man every nation of mankind to live on all the face of the earth, having determined alotted periods and the boundaries of their dwelling place, that they should seek God, in the hope that they might feel their way towards him and find him". Paul might well be taken to mean here that the general cultural history of the world is in itself a vehicle of revelation. History has been ordered such that there is potential for people to find God in it.
But note what the outcome has been: nobody has found God. "Yet he is actually not far from each one of us". All the reaching out and grasping that humanity has done, all the history of religion and philosophy, has only produced the altar to the unknown god. All the worship has only produced temples made with hands, containing gods which cannot move or act or speak. Human culture, religion and philosophy has by-passed the God who not far from each one of us, seeking a different god, a 'better' god, a god more to our taste. The conclusion of this history is that the true God breaks in in Jesus Christ and calls for repentance. Note that it is precisely this seeking after god which the nations are called to repent of, in the light of the fact that God has decisively sought after them.
Is the Unknown God to be identified with YHWH, with the Father of Jesus Christ? Absolutely not. Paul speaks consistently from the standpoint of revelation here - i.e. from the standpoint of faith in Jesus Christ and the Scriptures which testify to him. His critique of idolatry is derived thence, as is his interpretation of history. From that standpoint, Paul sees the void represented by the unknown god as the evidence of the absence of revelation, and he proceeds to proclaim Christ.
P.S. Any attempt to see broader revelation here actually leads to a very muddled concept of revelation - it is revelation that does not reveal, revelation that leads to unknowing. The sign of the unknown god bars the way to any such doctrine.