(Scalable Vector Graphics)
You can change Nokia phone graphics for the S60 phones (using SVG) in the Carbide.ui Theme Edition.
SVG has many advantages over the bitmap graphics. For example size of the file, scalability (making image bigger/smaller) without image distortion.
For editing SVG you can use either commercial (for example Adobe Illustrator) or open source (for example Inkscape) SVG editors.
http://inkscape.org/ -- Inkscape If the AknIconUtils::SetSize functions doesn't seem to work with svg created with Inkscape, you may need to add viewBox attribute manually to svg element.