BuddyPress.org

using @r-a-y ‘s super simple method

function my_default_get_group_avatar($avatar) {

global $groups_template;



return '<img src="http://locationtomygroupdefaultthumbimage.gif" class="avatar" alt="' . attribute_escape( $groups_template->group->name ) . '" />';

}

add_filter( 'bp_get_group_avatar', 'my_default_get_group_avatar', 1, 1 );

replace with proper src attribute (no idea if that works – just typed it up) – this only replaces the big thumb though, the smaller thumb on the forums index is filtered on bp_get_the_topic_object_avatar