I'm running FileMaker Pro advanced 126.96.36.1995 and FileMaker Pro Advanced 188.8.131.52. This morning, I downloaded a file with a custom icon from my development folder. After I unzipped it, renamed it and went to upload it to FileMaker server, I noticed the custom icon had been replaced by the standard FileMaker 16 folder icon.
After that I created a new file using both versions from the started solutions. In FileMaker 15.0.2 and earlier these would have a custom icon. In the versions above when you open the the first time they show the default FileMaker 16 folder icon.
If I click open and the list is showing the Recent list, the custom icon shows. Clicking browse and looking for the file shows the 16 folder icon.
Looking at the attached pictures check the icons for Tasks.fmp12 and Contacts.fmp12. In the recents list they show the custom icon in the open they don't.
When I upload one of the these files to my FileMaker development server FMS 184.108.40.206 it shows the default FileMaker 16 folder icon.
On FMS files that had the icon changed in FileMaker Pro Advaned 15.0.2 and earlier still show the custom icon. If I download them from the server and then try to upload them again, the custom icon no longer appears.
Note: All files being uploaded to FMS have to be uploaded using FileMaker Pro Advanced 15. The sharing feature in 16 will not let me enter user name or password so it is unable to upload to my 15 server.