Finder icons without thumbnail preview and a cross?

Solution 1:

Although it looks 99.9% complete, I think the Mac still thinks they are being copied over.
The 'thermometer' at the bottom of the icon would suggest this; the x at the top is so you can cancel before the operation is complete.

I'd try a reboot & see if that fixes it, otherwise try copy over again, maybe to a different folder.

If you were to look at them in List View, then the thermometer would be to the right of the file name, as either the same type of icon or as a 'pie chart', depending on version of macOS
Two views of a partially copied file, Icon & List.

^{These were done with Apple Remote Desktop, so the X is in that app's interface, not on the icon.}