Description of category allows any html/css/dhtml
and that's really great feature.
But what about a category image to display into block menu?
1) Add an image to category description field.
2) Edit Block : pico_block_menu.html
Replace
<a href="<{$block.mod_url}>/<{$category.link}>">
<{$category.title}>
</a>
With
<a href="<{$block.mod_url}>/<{$category.link}>">
<{$category.desc}>
</a>
Have Fun !
^^'