This will be easier using css and that way you can upgrade the plugin without problem. Other options are:
to activate the tools widget, that will remove the navigation and will allow to use a widget to place the navigation where you want it. settings > Tools Widget
to use Image store API to remove the navigation, add the following code to your functions.php file
function mytheme_remove_main_imstore_nav($nav){
return array();
}
add_filter('ims_subnav', 'mytheme_remove_main_imstore_nav');