Here are several services for different aspects of creating your book for self-publishing that I personally have used and feel comfortable recommending based on the quality of the work.
Cover Creation: Fay Lane
Fay is a freelance artist that creates beautiful covers for eBooks, Paperbacks (with the wrap), Audio, and box sets (See my "Wilders Complete Trilogy" box set image). She's easy to communicate with and all of her covers are eye-catching and alluring! Fay also has a great instagram page if you want to scroll through some of her pre-made covers there. You can get pre-made covers that you purchase from her, or you can work directly with her to have her create your own custom cover.
Book Formatting: Nicole Scarano
Nicole formats for a variety of publications (paperback, Kindle, Nook, etc) and is able to create and add custom images (think chapter headers, even some larger images if you want them on the opposite page of new chapters) to make the interior of your book clean, gorgeous, and genre-specific. She formatted the 2020 Autumn Nights Anthology, and I've used her professionally for other projects as well. She'll get the job done well, and you'll love how your book looks as you flip through it!
Graphics: Black Cat Graphics
This service offers graphics for ads, social media headers and posts, as well as website design and book formatting. The ads and banners always look amazing, and I've seen a lot of them around for all kinds of genres. Looking to get the word out about your book? You won't go wrong using this service!