I discovered Michele Albert when she joined an online discussion about using 3D programs to design cover art and illustrations for her books (both printed and ebook).
Went to her site and found a blog dedicated to her trials, tribulations and triumphs as she continually hones her illustrative skills.
She’s done some great work, and you can pick up some good tips from her commentary.
Check out her blog HERE!

Hello,
Thanks for linking to my experiments (and adventures!) in cover making. It can be a challenge. I’d love to exchange ideas, tips, etc. with anyone else using these kinds of resources for ebook covers.
Michele