Well iphones save images as jpeg files instead of png which basically lowers the quality of the picture.

I think there's some applications you can use to download and upload an image from inside the application itself so it stays as .png file but I'm not sure which apps can do that for you since I just use a pc to upload


So if able to I highly suggest using a pc instead.
But if that's not possible then I guess you could ask around if someone knows a good application to upload heads/bodies or something.
Someone on here might know an application which can do it but you'd have to hope they reply to the thread