Before submitting a cover request, please research your market. Custom covers are accepted on a case by case bases.
Head to Amazon, and browse a few of the categories you believe your book could be a best seller in. Find two books that you think a reader would say “this cover reminds me of ‘your book’, so I know I’ll love it”. The goal of a cover is to trigger readers into being reminded of similar books they read and loved.
The cover should not be reflecting a specific scene in the book, but instead display the key themes that align with other best selling covers.