It's not ideal, but hypothetically someone could write a Connect IQ watchface that just displays an image with no other information. Unfortunately it's not a low barrier to entry for writing CIQ apps, even if the app itself is very simple.
Alternatively, you could try this online watchface builder:
It's a 3rd-party project which lets you build a Connect IQ watchface app -- without coding -- that can be sideloaded to your device (you get an app file which can be copied to your watch by connecting the charging cable to a computer.)
Looks to me like you should be able to make a watchface with just a background image but no time or other data.
