I was able to squeeze some more optimisation out of it: For example: 600px-A20-OLinuXino-LIME2.png is 34,689 bytes as served by the site. Running it through P

I was able to squeeze some more optimisation out of it: For example: 600px-A20-OLinuXino-LIME2.png is 34,689 bytes as served by the site. Running it through PNGOUT, OxiPNG, AdvPNG and PNGCrush (all set to lossless) reduces the filesize by 6.8% down to 32,322 bytes with no visible diff to the image. I guess you'd need to weigh up the energy cost of compressing the image versus the cost of serving them all ~6% larger every time.