Wow - beautiful top!
I like the suggestion of doodling first. I saw an episode of Fons and Porter where Ricky Tims was a guest. He said if you can draw it with a pencil, you can quilt it. So, get comfortable with "pencil" quilting, then try on a practice sandwich until you are comfortable. I'm not an expert, but this is what I like doing.
I have also bought several practice quilting panels from the LQS to practice different designs. I was told by their expert quilter to use it several times, just change the color of the thread everytime I practice.
Please post a picture, all of us would love to see it!