The non-PHP expert has worked it out by himself, the category requires at least one post to work ( I presume it is the same for pages ) for reference here is the code:
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<?php if (in_category(‘2’) ): ?>
<img src=”path/image2.jpg” alt=’Category Name’ />
<?php elseif (in_category(‘3’) ): ?>
<img src=”path/image3.jpg” alt=’Category Name’ />
<?php elseif (in_category(‘4’) ): ?>
<img src=”path/image4.jpg” alt=’Category Name’ />
<?php else : ?>
<img src=”path/otherimage.jpg” />
<?php endif; ?>
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