Is default ICS wallpaper optimized for battery longevity?

So I've had this interesting experience recently and have been wondering if anyone else noticed this and could corroborate.

The Story So Far

I installed Cyanogen 7 on my Nexus One not too long ago (5-6 weeks). As part of the installation I also put an Ice Cream Sandwich theme and have downloaded a pack of ICS wallpapers, among them that "famous" one that has been featured on all the screenshots - you know the one.

Wallpaper_chroma_medium

via androidcommunity.com

After the installation I have noticed a somewhat improved battery performance, which I attributed to Cyanogen. About two weeks later I got kinda bored with the wallpaper and decided to switch it to another image from the ICS pack, this one.

Wallpaper_outofthebox_medium

After I did this I noticed a hit in the battery performance. At the time I didn't make the connection to the wallpaper because I also installed a few new apps right around the same time. In any case, the battery was doing crazy bad - whereas before it would drop to 60-70% by the end of the day, now I couldn't get through half a day without hitting those numbers and by the time the evening rolled in it would be hovering at around 10-15%. Since I thought it was some app, I removed any recent ones I downloaded but it didn't help. I also considered that the battery itself was dying.

In any case, eventually, after about 2 weeks of this I figured I'll try a different wallpaper. My thinking was, this was a very bright wallpaper and all those pixels were eating up the battery, so I tried a darker one, this one.

Wallpaper_architecture_medium

This had almost no effect. My battery improved ever so slightly, and I'm not even sure it was real, could've been a placebo effect. At first I decided that the problem had nothing to do with the wallpaper, after all I now had a much darker one and it had little to no effect. Still, two days later I thought to myself, "to heck with it!" and switched back to the default ICS wallpaper, and lo and behold my battery immediately improved, getting back to the old performance levels.

So What's The Deal

Is it possible that the default wallpaper is somehow "super optimized"?

Now, I understand that using a bright wallpaper vs. a dark one would affect the battery but I can't believe it would be this much (5-10%, maybe 15% difference yeah, but going from 70% at the end of the day to 15% - that's just mad). In fact, I have used many different wallpapers in the time I owned N1 and have never noticed this kind of difference in battery performance. I also realize that the default wallpaper has many more "black" pixels than that blue one but still, it's not like those pixels are completely off are they? So again, I just can't see how that kind of difference would come from simply the difference in the images.

The only thing I can think of is, what if somehow the default ICS wallpaper is specifically optimized for a PenTile display. Since PenTile displays have a non-even spread of the RGB sub-pixels (i.e. where the number of sub-pixels per each colour is not the same) maybe it's possible to compose an image that would somehow cause a specific pattern of brightly lit vs dimly lit sub-pixels that would be much more optimized for battery longevity than some other pattern.

Am I being crazy here? Am I over thinking things and it's much simpler than that?