What you are requesting is not available in 1.4. What you need to do is remove the button from the interface for regular users:
displayimage.php:
find
function html_picture_menu($id)
{
global $lang_display_image_php;
return <<<EOT
<a href="#" onClick="return MM_openBrWindow('picEditor.php?id=$id','Crop_Picture','scrollbars=yes,toolbar=no,status=yes,resizable=yes')" class="admin_menu" >{$lang_display_image_php['crop_pic']}</a> <a href="editOnePic.php?id=$id&what=picture" class="admin_menu">{$lang_display_image_php['edit_pic']}</a> <a href="delete.php?id=$id&what=picture" class="admin_menu" onclick="return confirm('{$lang_display_image_php['confirm_del']}'); return false; ">{$lang_display_image_php['del_pic']}</a>
EOT;
}
change to
function html_picture_menu($id)
{
global $lang_display_image_php;
$ret = "<a href=\"#\" onClick=\"return MM_openBrWindow('picEditor.php?id=$id','Crop_Picture','scrollbars=yes,toolbar=no,status=yes,resizable=yes')\" class=\"admin_menu\" >{$lang_display_image_php['crop_pic']}</a> <a href=\"editOnePic.php?id=$id&what=picture\" class=\"admin_menu\">{$lang_display_image_php['edit_pic']}</a>";
if (GALLERY_ADMIN_MODE) $ret .= "<a href=\"delete.php?id=$id&what=picture\" class=\"admin_menu\" onclick=\"return confirm('{$lang_display_image_php['confirm_del']}'); return false; \">{$lang_display_image_php['del_pic']}</a>";
return $ret;
}
And then to stop the deletion if the url is manually entered, find in delete.php
} else {
$query = "SELECT {$CONFIG['TABLE_PICTURES']}.aid as aid, category, filepath, filename FROM {$CONFIG['TABLE_PICTURES']}, {$CONFIG['TABLE_ALBUMS']} WHERE {$CONFIG['TABLE_PICTURES']}.aid = {$CONFIG['TABLE_ALBUMS']}.aid AND pid='$pid'";
$result = db_query($query);
if (!mysql_num_rows($result)) cpg_die(CRITICAL_ERROR, $lang_errors['non_exist_ap'], __FILE__, __LINE__);
$pic = mysql_fetch_array($result);
if ($pic['category'] != FIRST_USER_CAT + USER_ID) cpg_die(ERROR, $lang_errors['perm_denied'], __FILE__, __LINE__);
}
and replace with simply this:
} else {
cpg_die(ERROR, $lang_errors['perm_denied'], __FILE__, __LINE__);
}