In what way are they shot? Are the colors off, or are they badly cracked?
If the colors are far enough off, then scanning and reprinting to inkjet decal paper may be the way to go. If they are cracking, apply decal film over them.
Inkjet decals are best for dark decal designs to be applied over a light paint color. Use of white decal paper to make light colored decals to go over dark paints is possible but quite a challenge.
There is a Decal forum down below in the Tools, Techniques and Reference Materials section that you should check into. Lots of posts there on both inkjet decals and on use of decal flim.
I use decal paper from Micro Mark. I like it a lot better than the Testors stuff.