For the left hand, I was working on a ballad stride feel. I mostly play root/5th or root/7th on beats 1 and 3. On beats 2 and 4 a played crunchy cluster voicings (lots of 2nds!). I love to use this sound, especially on pop progressions. For a major triad, I'll often play the root and 9th right next to each other. For a minor 7 chord, I'll play the third and 9 next to each other or the third and 11 (or all three!).
For the improvisation, I decided to vamp the IV, I/3, II-7, I progression and treat it like a little mediation. I was really inspired by Bill Evan's beautiful solo piano improvisation called "Peace Piece." You may be able to hear the influence?
I hope you enjoy it!