[ATDrake]

Well, technically the alt text is supposed to be for the benefit of the blind and put in a short textual equivalent or description of what your image represents for those who can't see it (e.g. alt="My Book Title").

But aside from that, yes*, and now you need an <item> in the manifest for each image that is expected to appear inside the finished book, with the appropriate media-type="" filled in.

* Assuming your first two images really are named exactly that and are not missing a file type extension which they might have in the actual filenames but not in the version listed in the html.