I haven't shipped eggs but I've been on the receiving end many times so I thought I add some egg packaging tips to this thread as feedback to shippers.
When using the plastic or cardboard egg holders, best result is to line the eggs with tissue, napkin, or simply toilet paper. This prevents the eggs from hitting each other during shipping. Once had a seller that used saw dust but there were many bigger wood chips also that left dents and cracks in the eggs. So that was just as bad as not using anything.
If nothing is used to help keep the eggs secure, the results are fine hairline spiderweb cracks. Usually unnoticeable to the naked eyes unless candled. In hopes to salvage these eggs, I usually cover the cracks with some woodglue.
I don't have my good camera at the moment so sorry for the bad quality. Here is a picture of a little flashlight under one egg, among many others, that have these cracks from colliding with each other during shipping. Sorry it's hard to make out.