mmmh this thing is giving me headache and I can find an answer.

IPhone and IPod touch always apply a compression to every image format you upload on the device. That's not so good when the image is a pixel art piece. Trying to use a PA piece as Wallpaper seems impossible even setting the size of the image to a fixed HVGA 3:2 (320x480px).

I've seen examples of PA iphone wallpapers: they are not exact while zooming in (there's a lot of resample on the pixel edges) but they look good at a 100% view.
Does someone know how to achieve that result?