I use the images for reference, as long as I can view the image, the format shouldn't be a problem. I prefer photos but good ones are hard to come by. Harder still is finding enough to flesh out a unit's worth of markings. Views of the sides, tops, and bottoms of the aircraft are welcome. Angled views are less helpful but of some use. I will not be printing any files that are sent as reference pictures.
Written documents, that provide dimensions, colors, and other info are also great (USAF Tech Order 1-1-4 comes to mind). I got lucky on a recent book purchase (WW2 topic). The book contained narrative that included dates, air actions, squadron aircraft code and serial number combinations, some aircraft names, and a few useful pictures of aircraft names and markings. My previous internet searches yielded a couple of b/w photos and some artwork, not enough info to make a decal sheet.
The following may provide some insight:
I work and print in/from LibreOffice. I don't work in Corel Draw or Illustrator.
As a military staff officer and civilian analyst, I worked with Harvard Graphics and Power Point. That's my graphics background. I hate making slides* but they are a necessary evil.
I started Miscellaneous Miniatures as a painting service. I started making my own decals because it was very hard to find decals for the projects I had/have. Selling decals was a way to help cover the cost of the printer but soon became the focus.
I use the pictures/images for reference so that I can see the colors, shape, and how it should fit, re-creating the images in Libre Office. Test print, check, repeat.
Cheers, Kevin
*making decal sheets is just like making briefing slides, a necessary evil.