SYMPTOM:
Excel exports display a blank space in place of an embedded image when the image is referenced using an absolute HTTP URL path in Strategy Web 9.x
Below is a screen shot of a document with an image in Strategy Web.

When the same document above is exported to Excel with the image embedded, the export appears as shown below.

STEPS TO REPRODUCE:
CAUSE:
This is a known issue in Strategy Web 9.x
WORKAROUND
If the image URL contains a space, replace it with the ASCII equivalent '%20' in the image properties.
ACTION
Contact Strategy Technical Support for an update on this issue.