I recently got this game here on GOG. I have so far played through the tutorials and have been practicing with the different weapons, recently started with the campaign, and I did buy the soundtrack. Excellent work all around so far. I was wondering, though, if any of the background artwork in the menus and campaign, such as the sub in port with the Ticonderoga in the background, the carrier attack scene in the launch trailer (haven't made it to that mission in the game yet), or the other various cool background artwork could be put in the goodies section of the game as desktop wallpapers? Is there anywhere else I can find them? Thanks.

Unfortunately NO,
because: normally they should be located in the 'default' game folder and accessible because modders can change these images.
However by looking in this 'default' folder, under

C:\GOG Games\Cold Waters\ColdWaters_Data\StreamingAssets\default\campaign\images

I see the folders are empty, meaning they are compressed in the game data files and not openly accessible. As said, modders can change them by puting other images in these folders.

Sorry it took so long for me to respond, but thank you for the information.