As promised by Nokia, they said they’d bring BT file sharing to Lumia as it wasn’t yet a standard feature for WP7. Whilst you’d need to have a WP7.8 device (upgrades coming soon or you can install get the ROM on Navifirm at your own risk).
The app is available at the store link below. I’m not sure if this will integrate nicely into the share options or whether you have to open up the app specifically. There’s a section specifically for Pictures/Files. I am not sure either what file limitations if any are present.
Note: BT file sharing (and NFC tap to share) is already available for WP8 Lumia by default.
Cheers Viipottaja for the tip!