This made me realize that anything you generate using an /icon will contain DMI header data, which is far from ideal when you're generating something that's not a DMI file, especially if you plan on working on the image elsewhere (lets face it, BYOND's ability to scale images sucks)
I suggest the ability to set a flag that'll determine what image format your final result will be when saved to a physical file via fcopy() or ftp() (or similar)
icon.image_format = ICON_DMI // ICON_PNG, ICON_BMP, ICON_JPG, ICON_GIF
Perhaps?