NCM Firmware Repository File Extension

The Firmware Repository looks like a good idea to me.

What I haven't worked out: the admin guide says "Click Scan Firmware Repository to see the latest image files. By default, all files with the .bin extension are displayed".

What happens to the rest? Are they excluded from this feature?

I've scanned my repository a few times, but only .bin-files are shown

Where can I configure "valid" extensions?

I'd be glad if somebody could enlighten me.