If you fill a shape with a picture (right-click and select Format Shape), the picture will not get imported with the shape when you import the question into another quiz.
This is a known issue. Currently, the only workaround is to manually fill the shape with the appropriate image file after importing the question into a new quiz.
For reference, you can fill a shape in Quizmaker with a picture in the following manner:
- Open the question for editing, and switch to Slide View.
- Right-click the shape, and select Format Shape.
- On the Fill tab, select the radio button for "Picture or texture fill".
- Click the File button.
- Browse to and select the appropriate image file, and click the Open button.
- Click the Close button to save your changes.