The cloud of witnesses isn't limited to famous believers from the bible. Every believer who has gone to be with Christ is in the cloud of witnesses because a witness is someone who believes in Jesus Christ, whether here on the earth or in heaven. Once when I was on a plane a mother and daughter were sitting to my right. As we chatted, the mother mentioned how her husband passed away the year before and she wasn't sure about their relationship before he passed, because it was a bit rocky.
After we spoke for awhile, I decided to close my eyes and rest for a bit. Suddenly, with my eyes closed and being fully awake, a man appears before me in the spirit, who I sensed was the husband. He looked like Jerry Garcia, who was the lead singer and guitarist for the music band, "The Grateful Dead". In my mind, I asked him if he was the husband. Without saying a word, he nodded his head, "Yes." Then, I asked him if he was mad at her and he shook his head, "No". Then he disappeared. I turned to the woman next to me and asked if her deceased husband looked like Jerry Garcia. Both their mouths dropped open and the daughter proceeded to take out her tablet in order to show me pictures of her dad. He looked like Jerry Garcia. Needless to say, they were both shocked and greatly encouraged when I shared with them what just happened.
Hebrews 11:39-40 through 12:2 give us some insight into the cloud of witnesses.
And all these, having gained approval through their faith, did not receive what was promised, because God had provided something better for us, so that apart from us they would not be made perfect. Therefore, since we have so great a cloud of witnesses surrounding us, let us also lay aside every encumbrance and the sin which so easily entangles us, and let us run with endurance the race that is set before us, fixing our eyes on Jesus, the author and perfecter of faith, who for the joy set before Him endured the cross, despising the shame, and has sat down at the right hand of the throne of God. - Hebrews 11:39-12:2