Thanks for the questions Dave cos they are ones that many will be interested in.
First the same photo can be entered in many classes as long as it is appropriate.
Second, yes you can tart the pictures up if you want but nothing must be added like a toy, another cat, a bed etc etc. The pictures should be real not fabricated and the thing to remember is this is a cat show not a photo show, so I hope that peeps will judge the cats no matter the quality of the picture.Of course a totally out of focus or very dark or light picture where we cant see the cat, will not help the cats chances
Being a lousy photographer, I have loads of those kinds of pictures