You can use Corel to fix any parallax errors that come from an off-angle picture source...you can also use Corel to trace the rough outlines created by blowing up a small image, creating a smooth line that you can then make your masks (or a decal) from. It helps to have the image in Corel greatly expanded (like 10 to 20X) while you work on it. Here is an example of a graphic that I made from a rough source photo, and the trimmed and traced rough image that has been parallax corrected. Unfortunately the final print image is a Corel file format that can't be posted here.

You could also BUY the decal sheet from Twobobs, scan it, and scale up/clean up with Corel. This is the best method if a decal sheet is available for the scheme you want.

Barry