Hi Kris,
Hope your keeping well.
Step 1
I would recommend checking if 7975 phones are using correct phone load, if not you can download the SCCP75.8-3-2S load for 7975.
Step 2
Ringtones
Check if your Router have Ring List XML file in flash -- flash:ringtones /RingList.xml and flash:ringtones/DistinctiveRingList.xml
Or
Flash:DistinctiveRingList.xml and flash:RingList.xml -- I am not too sure which file 7975 is looking. You can use the debug tftp event to find out what 7975 is looking
TFTP Command
tftp-server flash:ringtones/RingList.xml or
tftp-server flash:RingList.xml
tftp-server flash:DistinctiveRingList.xml
Step 3
Background Images
Cisco 7975 IP Phones looks the List.xml file in Desktops/320x216x16/ folder, if you have 7970 background images on the router it will be saved in Desktops/320x212x12 - the best way is to copy the List.xml file from Desktops/320x212x12 to Desktops/320x216x16/
Make sure that you have tftp command -- tftp-server flash:/Desktops/320x216x16/List.xml
For trouble shooting use debug tftp event and on the IP phone web page - check the console logs
Hope this helps, please do let me know your finding.
Regards,
Kazim