http://www.cisco.com/en/US/docs/voice_ip_comm/cuipph/7975g/6_1/english/administration/guide/7975cst.html, which explains the requirements for the background image for the 7975G phone, seems to have contradicting text:
Configuring a Custom Background Image
Step 2 Upload the new PNG files that you created to the following subdirectory in the TFTP server for the Cisco Unified Communications Manager:
while in another section:
PNG File Requirements for Custom Background Images
The PNG files for background images must meet the following requirements for proper display on the Cisco Unified IP Phone:
•Full size image—320 pixels (width) X 212 pixels (height).
•Thumbnail image—80 pixels (width) X 53 pixels (height).
So, which is it? 320x216 or 320x212? And is the thumbnail size correct too?