<a id="pointmap"><img src="{% static "static/style/pointmap.png" %}"></a>
#pointmap:hover {
background: url(mapvi.jpg);
width: 300px;
height: 300px;
position: fixed;
top: 10px;
left: 30%;
}
<span style="position: absolute; left: 820px; top: 63px;">
<a onmouseout="document.getElementById('pop-up-map').style.display='none'" onmouseover="document.getElementById('pop-up-map').style.display='block'" target="_blank" href="https://yandex.ua/maps/?lang=ru&ll=30.325693%2C50.172746&z=18&mode=whatshere&whatshere%5Bpoint%5D=30.326832%2C50.173075&whatshere%5Bzoom%5D=19">
<img src="{% static "static/style/pointmap.png" %}">
</a>
<span id="pop-up-map" style="position: absolute; top: -30px; left: -318px; display: none;">
<img src="{% static "static/style/mapvi.jpg" %}">
</span>
</span>