I think I need to be more precise. They are files created from the database app FileMaker Pro. I have quite a few of these, one for finance, one for cycling etc etc and each has been given its own icon representing its content. They are stored in the ‘Documents’ folder on both machines which uploads any changes to the iCloud so when you open either machine it automatically downloads the latest file from the iCloud. I hope this makes it clearer
I am afraid I do not understand your question. Possibly the simplest way of explaining this is that when I change the icon of a shared file, as long as I am working on thecomputer it was created on there is no problem. However, if I open the shared file on another computer the icon is replaced by the original.
As explained before the machines in question are both mac and the shared drive is iCloud
If this is the case I think iCloud is not designed to support MacOS icons because Image2icon create and apply icons but can't be considered responsible for moving the icon from different machines but, if you can find a method which preserves the icon I'll be glad to fix Image2icon in order to support iCloud.