I'd also really appreciate some hex color recommendations for the sky, which is pretty sickly. Phase of the moon would be harder to do, but it wouldn't be impossible. Please email me if you have suggestions for improving the Digital Stump. According to several reliable sources, the safest colors to use in web graphics are those for which each component is a multiple of 51. I've reassigned the colors in the stump generator so they are less likely to dither on 256-color systems, but the colors now look worse than ever.
Suggestions are very welcome.
At that time, I will probably also find a way to generate an animated gif of the recent stumps to provide a 24 or 48-hour loop. Time will tell. That's a very good question. I went through several icon designs before I decided to use a stump. The original stump was hand-painted in xpaint.