After concept (What is this image about? What do I want to say? Why am I moved by this?),
composition (or ‘design’) is the most important thing on the list of 7
(concept, compo, drawing, values (tones), edges, brushwork, color)(not all relevant to photog).
There are some basic rules (eg don’t center the subject, pay attention to the corners of the image space, beware of cutting things off at the wrong point, etc. (listed in most books about compostion). – that should become pretty much second nature),
and the idea of dividing the picture space into thirds and siting important things on one of those intersections, etc. (again, listed in most books on composition – I should think most photography manuals have a good section on this/composition in general).
BUT, the real big things are:
1) to have interesting shapes arranged in an interesting way (and most usually avoid repetition/repetitive elements unless you’re SURE you want them)
and, ABOVE ALL,
2) consider the light/dark pattern (in Japanese the ‘NOTAN’).
Painting and photography are above all studies of light… …and there are no ‘rules’ – they are only the struts on the launch ramp! guidelines maybe?
This, in fact, means that the important aspect of a representational image is the abstract aspect – all images are abstract art!!!