After having several conversations with another artist, I finally decided to improve the appearance of my renders using GIMP.

I admit that I'm a complete beginner with this program, so I was only able to apply some standard settings.

I also included the original, darker render that I modified, as well as a brighter version that I ultimately did not use.

As you can see, the improvement is minimal, but I recognize that this is primarily due to my lack of knowledge about how to effectively use the software.