I made this illustrated book cover 2 years ago after learning how to really work with the pen tool. I created everything in the image (minus the text) with the pen tool, so I thought it would be fun to reinvent my design without the pen tool!
I created the petals by overlapped two ellipses, and used pathfinder's intersect to create the shape. I also decided to use gradients, which is something that I never use in my designs. I then duplicated and rotated the petals to the centre... and then duplicated and reflected it to create a symmetrical design (also something I never do)
I then drew some clouds which were ellipse and rectangles that I warped with: fish, flag and arc.