Asher, self-promotion is not allowed in this forum so I'm not sure this is the right place to ask for this. I recommend a Google search, there are tons of pro services out there that provide this kind of service at a reasonable price.
Have you considered searching for a relevant photograph? I use iStock.com to find a photo that I can use for a course image. Of course, Udemy will do this for free for you, but I have found that they don't exactly get what I want to convey in a course image that reflects the content of my course.
@AsherRubin I use a combination of stock pic and vector graphics free from Pixabay.com, I then import and edit them into something unique that (hopefully) tells my story on another free site Canva.com. It is fun and helps me stand out from the crowd.