I made all by myself
I'm more experienced as an artist than a writer, plus I'm too broke to actually pay someone. When you make all your shits yourself, you own it 100% and can commercialize it as you want without needing to pay.
In real life, I occasionally design covers for an indie publishing house.
This is my thumbnail, it uses my own art.
The title is my own handwriting with default brushes.
This is my banner, only a little modification was done.
This is my full cover, with different concept and art.
Tips: If you're broke or can't make cover yourself, just use free editor like Canva, PicsArt, or Snapseed. Be sure to look for free to use stock photos; pexels, pixabay, and PNGtree is quite good option. Always look for term of service and license of things you use, especially if you meant to commercialize it.