A lot of guys beg borrow or steal a very high-megapixel camera and take Overhead shots. One big one for reference, and then detail shots. From that, you can put a good image together.
this involve a lot of work in order to reconstitute the full puzzle.
on of the most common problem with this approach is the paralaxe problem. most photos are taken with a small angle regarding the subject, it's quite impossible to have a perfect perpendicular shot when you try to have overlaping shots.
generally the various closeup are slightly "angled". thus the reconstition loose accuracy.
but i aggre it's better than nothing.
eg I have some hi-res pics of a sideinvader sideart, that are angled. I must admit that reconstituting the whole image is over my skills. if someone is volunter
spaceinvaderssideart_Folder.zipscanninng huge pieces, as the whole sideart of a cab, is a difficult job that inolves a lot of energy and time:
tracing a grid on the artwork (usefull for the puzzle assembly), overlaping scanning. but we need people doing that.
in order to provide good source material for tracing.