The idea of this theme is to show the extremes of your Cav's personality - both angelically good/sweet and very, very bad/evil/plain mad. Two sides of one coin, if you will.
If you have an image of two photos joined, you may submit that, or, in this case, two photos. However, they must be of the same dog (the theme makes no sense, otherwise) and the two photos count as one entry. Since some people will be submitting two photos, please make sure that you submit two medium size photos rather than the default largest that flickr gives - just to save on bandwidth/loading time... never to mention it's easier on the eyes for those of us with small screens!