If you intend to write romantic-styled piece, You may want a good melody to start the piece, like a singable theme which the listener can easily recognize throughout the piece. By good melody, in my humble opinion, should have "up's and down's" and good contrast other parts of the music. There are some horizontal motion but it is rather oblique and it does not stand out much from the accompliment. You may think it as a opera singer singing passionate tunes and interact with the orchestra. I would also expect more chromaticism in both the baseline and the melody. Candences. I would expect a stronger sense of cadences for the phrases in a romantic piece. It is like journey - you need some rest between the beautiful scenaries so you can stay energetic and focused. Your improvisation seems more modern to me as it reminds me of the never-ending minimalistic music with non-diatonic (non-triadic) lines. For the variety part, you may want to try with Change of tempos Change of baseline rhythms Change of scales/ modality ("colour") Change of timbre (high vs low register of the piano) Change of texture (Density of chords)