¿Has probado bien en el archivo css de k2? A partir de la linea 325
/*----------------------------------------------------------------------
Component: Itemlist view (category)
----------------------------------------------------------------------*/
div.itemListCategoriesBlock {}
/* --- Category block --- */
div.itemListCategory {background:#f7fafe;border:1px solid #ddd;margin:4px 0;padding:8px;}
span.catItemAddLink {clear:both;display:block;text-align:right;padding:4px;margin:0 0 4px 0;border-bottom:2px dashed #ddd;}
span.catItemAddLink a {}
span.catItemAddLink a:hover {}
div.itemListCategory img {float:left;display:block;background:#fff;padding:4px;border:1px solid #ddd;margin:0 8px 0 0;}
div.itemListCategory h2 {}
div.itemListCategory p {}
/* --- Sub-category block --- */
div.itemListSubCategories {}
div.itemListSubCategories h3 {}
div.subCategoryContainer {float:left;}
div.subCategoryContainerLast {} /* this class is appended to the last container on each row of items (useful when you want to set 0 padding/margin to the last container) */
div.subCategory {background:#f7fafe;border:1px solid #ddd;margin:4px;padding:8px;}
div.subCategory a.subCategoryImage,
div.subCategory a.subCategoryImage:hover {text-align:center;display:block;}
div.subCategory a.subCategoryImage img,
div.subCategory a.subCategoryImage:hover img {background:#fff;padding:4px;border:1px solid #ddd;margin:0 8px 0 0;}
div.subCategory h2 {}
div.subCategory h2 a {}
div.subCategory h2 a:hover {}
div.subCategory p {}
Tambien es posible que sea mas cuestion de los estilos de tu plantilla joomla.