Jia, explains that you shouldn't place any objects in the center of your piece unless you have a story for it, because that will effect the composition of the painting and lead the eye some where else. He explains that you would need to create several more and to make these shapes turn and have value changes while still holding up the values of the design and composition stay the same. here is an example of what he meant and how he actually changed my painting. He gave me advice not to use to much light until the end and use a 20 or a 15 as your lightest, while curves are great if you need to adjust the values quickly.