OK, for 4.2 in skin1/customer/main/subcategories.tpl (it is different) find and comment out..
<h1 class="category">{$current_category.category}</h1>
or depending how you have your store set up....
<img class="subcategory-image" src="{$current_category.icon_url|amp}" alt="{$current_category.category|escape}"{if $current_category.image_x} width="{$current_category.image_x}"{/if}{if $current_category.image_y} height="{$current_category.image_y}"{/if} />