I've just set up a new Mac with a fresh install of Yosemite 10.10.5 on an erased hard drive, and then installed only FileMaker Pro 13.0.9 and 14.0.2. When I installed plug-ins, done both by dragging or by scripted installation (into the alternate Extensions folder) the plug-ins do not have the familiar icons I'm used to, instead they just appear as folders. This hasn't happened on any other machine here, but those all have had a long history of running FileMaker version after version, so I'm supposing it has something to do with starting with a clean slate.
Is this a known issue? I've tried numerous things to get the icons to show up. Copy-and-paste of icons from inside the Get Info window works, but that's cheating. The plug-ins DO work, however.
Screenshots of a normal computer and the new one supplied below.