Great result, congratulations. I see you've been busy while i was catching some ZZZZZ's downunder huh!

Yep, if a 'bricking' is due to a corrupt IMG file it is most often one of the detail maps (gmapprom.img; gmapsupp.img; gmapoem.img) in the Garmin folder which has caused the problem. Very rarely is it the basemap (gmapbmap.img) as it was for mylona79 in the old thread, or any other ancillary map such as the time-map (gmaptz.img).

Is that a complete list of all files/folders within your DNX's Garmin folder?

I'm asking that because on checking specs it's clear that, unlike the senior model 9260BT, the 7260BT doesn't have ASR (automatic speech recognition) capability, nor can it use gmap3d.img for 3D buildings view in cities, however it can show JunctionView images so along with other usual folders there should have been a JCV folder within the Garmin directory with *.jcv files specific to that gmapprom detail map. A JCV folder should also work from a Garmin folder of the SD card however, so if you want to use that feature with the replacement map you can put that folder in SD:/Garmin too. That will very much depend on Garmin having issued device-appropriate JCV files matching their EU NTU mapping because your device uses the JCV file-type for the very old nuvi 7x5W devices dating from ~2008 ....so you may not even be able to get JunctionView to work anyway.

About using files on a media card generally: Note that perhaps only gmapsupp.img naming may work for a detail map in SD:/Garmin. Perhaps other naming limited to 11 letters (e.g. "anyname.img") might working in SD:/Map folder but i doubt it seeing the unit's internal file structure is of the older type (there isn't a ".System" folder present and maps are in the Garmin directory). Also that style of Garmin device exclusively used NT format detail mapping and Garmin has now discontinued NT for European maps, issuing only NTU format (capable of displaying Unicode characters) so if you have a problem getting an NTU detail map img to display properly there is a workaround by changing the CP number which may work if the most recent firmware from January 2014 (V4.31) doesn't support unicode and causes navigation guidance problems.

N.B. The *.sum files are only checksums and can safely be removed.

This thread can now serve as a guide to others with soft-bricked black display DNXxx60BT units. To me the method i suggested and which you've proved is easier to follow than the one in the earlier thread. That might be just as effective, however what's been used here is the more traditional way of restoring soft-bricked Garmin devices. I've put a link in the initial post of that thread linking to your post there to save others wading thru to find it.