Thanks for the feedback, guys! You were definitely right, it was too dark.
I was unable to get a better feel working without resorting to shaders. So now I'm a little more flexible, AND have to offer a new option in the menu screens. GOSH.

Anyway, I'm still struggling a little with the night-settings. I assume this is still too dark, though I found it perfectly playable. Then again, I've been playing this game for a while now, so perhaps I'm not the best judge of that.



Here are two other settings. Here's a fire dungeon:



And here's an evil dungeon. Everyone knows that violet is the most evil color.





@Superku,
thanks also for the gradient feedback!
I'm planning on trying to use simple skycubes (also mostly gradients, I suppose, but we'll see) now.
I'll have to create a mockup or two to see your ambilight-idea in action, but I'll keep that in mind!

@Hummel,
Yeah, I wanted to try ground fog anyhow. I'll post a shot when I get around to adding that!

@Joozey,
Thanks! I am not using draw_obj at all right now, but I plan on using it for the bright spots that mark room exits, entrances and the golden treasure chest.