Some of my files in Rox Filer have something odd on the top left of the icon, a sort of grey squirly thing. Screenshot attached.

Any ideas??

My guess would be a symlink

I thought so. Right clicking / properties just refers to them as inodes/directories so it doesn't look like a symlink.

I think some of them have changed recently, this is a new install of M11 reusing my /home directory.

It could indicate whether or not something is mounted.

You could look for it in the MIME folder for whatever icon set you're using. I'm assuming it will give you some clues as to what it means.