I, too, have had many images printed on fabric at Spoonflower. I have always been happy with their process. In all cases, I have used either the petal cotton or poplin. You may get a sample of your work first, which I have also done. It is worth the fee, which I believe is $5.00. I had a huge project and ordered their samples. Wow! They are awesome and I go to them whenever I need anything printed.
Your painting is outstanding. I love it!