I followed the code exactly from this example: Extracting Images from Presentation shapes|Aspose.Slides Documentation, except I skipped the background portion, as my slides don’t contain backgrounds. It also seems to be file specific, it only happens to a test powerpoint with one image in it.
I have tried understanding your requirements and have not been able to completely understand them. Can you please share what issue you are facing while extracting the shapes. Please share the source presentation, extracted file and desired output. We will investigate the issue further on our end to help you out.