Сева

function getNumber(dataRequest) {
  $.ajax({
    url: 'file.php',
    method: 'GET',
    data: {
        get_value_1: true,
                },
    async: false,
    success: function(data) {
      //...
    }
  });
}

<a class="link" href="#" data-img="img1.png">Link 1</a>
<a class="link" href="#" data-img="img2.png">Link 2</a>
<a class="link" href="#" data-img="img3.png">Link 3</a>

<div class="div1"></div>

var links = document.getElementsByClassName('link');

for (var i = 0; i < links.length; i++) {
    links[i].addEventListener('hover', function() {
        let img = links[i].getAttribute('data-img');
        document.getElementsByClassName('div1')[0].style.background-image = img;
    });
}