Same here. The following worked for us. Close all OpenOffice windows. Then re-open your document. Image are now showing. It seems to be related to a memory issue.
If that doesn't work here are two other solutions:
1. Post hoc solution: Open your document, press F5, expand "Graphics" section. For each of the images, right click and select: "Drag Mode > Insert a Copy". This ensure that a hardcopy of the image is used instead of a link to the image. Note that this might increase the overall document size.
2. Proactive solution: Do not use drag and drop or copy and paste of images into Impress. Instead, use Insert –> Picture –> From File. The important part is to make sure that "Link" is not checked.
In my opinion, the default behaviour should be to make a hard copy of the image with an option the create a link. Not the other way around. Or maybe an OpenOffice preference to set what works best for you.
source: http://www.robinbye.com/blog/2010/05/24 ... entations/