I do what you describe occasionally. My wife has bangs and I like to see my cum on it. She doesn’t like cum on her face though so I need to be careful when we do this.

Sometimes I also release my ponytail hold, go around her and release into the back of her hair. The sight of my cum on her soft, shiny, loose locks is a huge turn on, but is harder for my wife to enjoy (she also gets a thrill seeing my cum on her hair). The solution to this particular problem though is a boon - photos!

Most of the time though, from my ponytail hold, I will gather all her hair (some would have come loose while she was blowing me) and place it at the top of her head in a pseudo bun. Her hair is long and thick enough that the bun is quite high / tall. As I am doing this, my wife will lower her head slowly. I then make a hole in the bun as I insert my cock into it, and, putting it very crudely, fuck her bun till I come and shoot my load deep into the bun (while still holding on to her hair with both hands). Again, the bun is big enough that my cum is (most of the time!) contained within it. This particular way gives us both immense pleasure - for me as I like the control aspect of it, and for my wife too as she does have and enjoy mild submissive tendencies.

Hope this answers your question and gives you some of the spicy ideas you were after!