OK, I contacted LG directly after my last post and got this today. It's not really what we wanted to hear, but it is at least a response.
Thank you for your query regarding your LG TV; I would be more than happy to assist you with this query today. There is currently no option to change the screen saver images that come up when you have no signal going to the TV. We are looking into adding this feature on our newer TV’s and either updating the images or removing the screen savers all together on our older TV’s due to complaints of the dog setting off customers pets. We aren’t aware of when these changes might happen however as we have started looking into it recently.
I guess the firmware update with new images is addressing the annoyed pets issue :-)