In the next beta we'll see about removing the images from the new posts results. It is true that we have implemented them as threads, but there are a number of "threads" in the wiki that should not be considered articles: Images, Categories, Special Pages, Templates, Headers, Redirect pages.
These should all be excluded from getnew, as you have pointed out, because their content can tend to be created rather spammily (categories specifically - just create an article and put it in 50 categories that don't exist. Those 50 categories would now be getnew results).
As you can see this issue extends to the core VaultWiki product, so I am moving this issue to the project.