{exp:gallery:categories gallery="{gallery_name}"}
{category_row}
{row}
{exp:query sql="SELECT cat_folder, parent_id, cat_name, filename, entry_id FROM exp_gallery_categories c, exp_gallery_entries e WHERE e.cat_id= c.cat_id AND e.cat_id = '{category_id}' AND custom_field_one = 'yes'"}
{category}
{if category_description}
{category_description}
{/if}
({total_files}) files
{/exp:query}
{/row}
{/category_row}
{/exp:gallery:categories}