Scratch that enquiry!
I discovered that by copying the GIFs into the FMServerAdvanced Databases folder before I uploaded and opened the fmp12 files that the linked GIFs show up OK!
Apparantly you have put the GIFs in a global field.
Values in a global field are only current to the current user and they take the value of the server whenever a new client is logged in.
If you want to update a global field on the server without taking it from the server, you have to run a script on the server which updates
the global field to store the value on the server.
Hope that helps,
Ruben van den Boogaard