After viewing my newly cached images, on top of another solid layer, I noticed speckles showing on the imagery. These speckles turned out to be the bottom layer showing through the PNG's 'background'. Apparently a PNG's header info contains a single color that represents the transparent background.
In the process of caching, this background value is inherited from the background value of the source ArcMap document's dataframe. If not altered, the default is 253, 253, 253. After caching, every pixel with the rgb of 253, 253, 253 will be treated as transparent and therefore show any colors that are below it (in whatever application you are using your final cache in)
If you are displaying your cache directly over white, no big deal, if not, expect to see odd 'speckles'.
Since I am displaying my cache over another cache and there is some overlap, before caching I had to set my dataframe's background to something obscure and unnatural like rgb, 200, 100, 200 and hope that there weren't many pixels with this value.
I should also mention that there are settings in ArcMap to change the transparent color of your cache to 'none', but this may not help if you are not using ArcMap.
I'm writing this as a partial solution, only because there is not any info out there about this. Discussion and input is more than welcome.