Contour cut multiple images for large format printing

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.

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.