The image is sublimated directly onto the treated surface of the panel using special dye based inks. This makes then smudge proof and not likely to be scratched unless scraped with a hard or sharp object.
This is not recommended. The veneer has a coating which the image has been sublimated to. Some chemicals could potentially harm the surface.
White is not a standard color that is printed. Essentially when an image has pure white, no color is applied to that area. As the colors in an image get darker, more ink is applied. If your image has pure white, it will appear as transparent. That is where the beauty of wood prints come in since your underlying wood pattern becomes more visible the lighter the color.
You should not have do anything other than choose a size that matches as close to your image as possible.