I did this painting from my Mom's purple Iris. It is done in oils and on a canvas. It is available here for you
The Purple Iris measures 16"x8" and is perfect for you. I put greens,purples,yellows,and the siennas in the painting. The background is done with darker values of purples and blues.
Title Purple Iris
Medium oils on canvas
Size 16"x8"
Signed by Barbara Haviland
http://barbarahaviland.fineartstudioonline.com/works/502079/purple-iris