Whether others can see/access files in container fields depends on:
The version of FileMaker you are using.
The storage options specified in Manage | Database | Fields | Options for that field
The method used to insert/import the image (was store a reference enabled)
How the other users' computers are configured (in some cases a particular folder may need to be mapped/mounted exactly like it is on your computer)
So what version, options, methods, etc have you used with your container field?