I know this is not what you were looking for, but I had fun making this image anyway. Don’t feel like you have to somehow appease me. Normally I would get more information first, but I was like, f*%# it.
This is what I would call economical art. Silhouettes, simple palettes, minimal gradients. It’s vector art, basically, and fairly easy to produce. I only used polygonal shapes, actually. Silhouettes, when done right, can convey a lot of information, but still leave a lot to the imagination. It’s a good fit for most IF, I feel, because it also doesn’t distract as much, especially when next to text. Being vector also has the benefit of rearranging elements and changing colours with much more ease than bitmap graphics. SVG is also fully integrated in web-browsers, so even individual elements of an image can be altered or animated. Change the skin colour of a character? No problem.
The style you have currently is called painterly and while there are very talented artists who can speed paint to almost that quality within a couple of hours or so, it’s a big leap in skill level. I think it would take most artists considerably more time. That said, I dug out my old tablet and I’ll give the painterly style a go, but I don’t expect anything of real quality though. I’m not practiced. It’s just for fun.
For a text adventure of a serious tone, I would actually mostly focus on getting a good, unique looking font for the title. Something sharp and interesting. It would look great on it’s own in most cases. The horns and moon could be incorporated into the font to make a logo of sorts perhaps. Clearly, your game needs to be called Moondemon though.
Just FYI, the font I used is called Buckingham and is free for personal use only.
Anyway, I had fun. I hope others get inspired to share more of their time and energy with collaborative work, whether it’s art, chunks of code, music, RPG rule systems, or (heaven forbid) an awesome premise for a story.
Edit: I didn’t realize there was so much banding in the gradients. If you actually want to use this for anything, let me know and I’ll tweak it a bit and balance things a little better in the image.