With the rise of Retina displays people are looking for resolution independent alternatives to PNG icons. Some fell in love with font-icons, some are shouting “SVG”. But I’m sorry, if you’re looking for a silver bullet, I’m afraid it doesn’t exist.
A great deep dive into the current strategies used for icons these days. Personally, because of the lack of effects (and their non-CSS/HTML nature) I generally avoid SVGs, but will mix icon fonts and plain-old sprites as it seems appropriate.
Pretty sure this is already solved in android, due to the multiplicity of devices, resolutions, etc. It is called ninepatch.