Contour cut multiple images for large format printing

[Toya5FA2]

For my company, we submit multiple images on a 48x96" artboard for large format printing and contour cutting. I usually size and place the files (png) on the proper size, save as a .pdf and send over to the printer. They charge us to create the cut lines for their printer to read. I would like to learn to do this on my own as we're a small business and paying a pretty penny. 

I have found several tutorials on vectorizing and adding contour lines to single images but can not find any on doing this with multiple images of various sizes, on one board. 

Any help is appreciated. Thank you. 

[Jacob Bugge]

Toya,

Suitability/applicability of of original artwork as raster/vector aside, given PNG files that need to be contour cut you may consider this simple/primitive approach, which may be used for both single and multiple images:

1) In PS, open the (collection of) image(s) and apply the Image adjustments Brightness/Contrast at the lowest (maybe repeatedly) to create an image as black as possible,

2) In AI, apply Image Trace to create a single path enclosing the/each image(s), and Expand the Image Trace;

3) If needed to cut at a distance and/or to obtain a single contour for multiple images, select the enclosing path(s) and apply Offset Path with a positive offset value either corresponding to the desired distance or sufficient to obtain a single non Compound path enclosing all images with a suitable (not too irregular) but possibly excessive shape and no holes within;

4) If needed to counter an excessive positive offset needed/applied in 3), apply Offset Path with the negative offset value that gives the desired single contour shape.

[Monika Gause]

Are those PNGs already transparent?

Such as this (in Photoshop)

In that case in Illustrator in the Appearance panel you can try:

Add a stroke to it

Add the Effect > Path > Outline object to the stroke

Add Effect > Path > Offset path to it

When you're done: Object > Expand Appearance

And Object > Path > Simplify

One important thing: don't rotate the image until after the appearance has been expanded.