Change img src by alt
<script>
$('img[alt="Kůže 1"]').attr("src","https://code.kubanavratil.com/user/documents/upload/res2020/RedFir/Euphory.jpg");
</script>
<script>
$('img[alt="Kůže 1"]').attr("src","https://code.kubanavratil.com/user/documents/upload/res2020/RedFir/Euphory.jpg");
</script>