Don't use latest for images in the examples

[jorgemoralespou]

When deploying an application from the latest tag, at any point the application example we ship might break.

As an example, the mediawiki deploys latest, from a remote repository you don't control. Either use a tag, or expose the version as a parameter, defaulting to a value that can be changed at instantiation time. Add to the docs the tested versions, so a user instantiating the APB know if it doesn't work anymore, which tag he could use.

Just as an advice.