Hi Raymond, thanks so much for sharing your journey with the March contest. I totally empathize with your frustrations. Next time you're struggling with a concept, or on the fence about something, I would encourage you to share your WIPs. I've found that this has been a very supportive, safe and helpful community, and it's always good to get a fresh perspective.
Re: your thumbnails, the last one with the dead witch and her red shoes (only skirt, stockinged legs and shoes visible) would have been hilarious, bold and unexpected, and I bet you would have been able to render that faster than the concept that you had chosen initially (the characters traveling on the yellow brick road to Oz). Next time, I suggest you share your concepts at thumbnail stage and ask for help choosing. Even if you don't like any of your thumbnails, someone might say something inspired by your thumbs that sparks an even better idea or direction in your mind.
Lastly, congratulations on completing a cover illustration for the March contest! It's a bold, graphically simple solution and the falling, burning house silhouette is my favorite part. The overall feel is mysterious and dark. I look forward to seeing more of your work.