Add below Class CSS in Your CSS style with loading.gif image

.ui-autocomplete-loading{
background:url(‘https://3.bp.blogspot.com/-R10KlQEhZTc/WbOwpMZySlI/AAAAAAAAAGg/rOODPicyDeQEhEJYbOkXpi9Q4Sse3s-cgCLcBGAs/s320/loading.gif’) no-repeat right center !important;
}