This might happen if you are using ExtendSim 10.0.7. The application development framework used by ExtendSim had a bug in their software that could cause pictures/images on model worksheets to disappear. They have fixed the bug and the fix has been included in future releases of ExtendSim.
Please upgrade to ExtendSim 2024 or update to the final ExtendSim 10 release...10.1.1 to resolve this issue.