Keep on improvising. Many ideas were explored in this one. You can use this to build the relationship between piano technique and artistic expression. Eventually one builds a repertoire of ideas for improvisation, to which one can call upon when a particular expression may be desired.
One thing you can practice is taking an idea and expanding upon it.
I liked 9:28 oblique motion of line, with the gradual separation of hands and registers. Thanks for sharing.
What I do quite often, however, is to take some familiar motif (say, a theme from a movie), and play around with it. I can pretty much immediately play most simple tunes by ear and harmonize them, and I then experiment with them, adding extra voices, improvising additional melody lines, and occasionally reharmonizing. Does that count?
However, there is another aspect to music making, and that is taking your technique, your musical ideas and making them into pieces with some sort of structure. This is one of the next steps you can be working towards: musical focus. For example: I heard a lot of focus in your Frustration! improv. It was created around a central idea, and then you explored various perspectives on that idea.
When you refer to having musical focus, are you referring to having some kind of underlying theme, or are you talking about musical form?
Is it common practice to keep a musical structure in mind while improvising, as opposed to composing?
It is a slightly separate skill to improvise while keeping a structure in mind, say, an AABA form, and were you also suggesting developing that?