Another thing you have to be careful about is how you went about "naming" the article.
If you entered it as a URL, the page didn't exist, and clicked Edit, "test-photo.jpg" from the URL would be decoded in the form Title field as "test photo.jpg". Since it does not have the dash, the image filename no longer matches exactly with the title. This would pass validation, however, because "test-photo.jpg" and "test photo.jpg" resolve to the same location. However, using the image BB-Code would not show the appropriate image, and the image would not be displayed on its page after creation - the page would APPEAR empty, even though it exists (no "There is no text in this page" message).
Over the last several builds we made some improvements to title-attachment matching so that the image would show for this specific case.
However, these have just been theoretical fixes because we noticed the possibility existing in the code. We have not been able to duplicate this particular error without more information on the exact process of image creation that ended up failing.
Closing this as Fixed for now. I do not anticipate there being an issue once VaultWiki 4 comes out, because images will be stored with additional information over regular attachments.