So, when jumping back onto the project this morning, I decided that before I can do any more work on that spider, I'll have to sort these graphics out.
So, I spent the day manually downscaling each sprite (don't worry, there weren't many) from around the average 32x32-ish to about 16x16-ish. Large enemies go up to 24x24. I'm really quite happy with the result and the overall look of the game as it is.

Tomorrow, I'm gonna work on the spider enemy.