Hi,
You can edit the view "product | listing" and "category | listing".
In these views, you would find the line
<div class="hikashop_category_description">
Just below, you would see that the category image is displayed.
So, you can modify the option "show_image" in your menu/module to hide the image.
You can add a CSS rule in HikaShop for
div.hikashop_category_description img { /* ... */ }
in order to set rules on the image (and change his size).
You can remove the hml line in the view.
You can add some html in the view.
Regards,