Yes, it is possible. After you upload/submit the video you can choose autogenerated thumbnail images for your video:
or you can set your own image after your account gets verified:
The verification process looks like this:
If the video is not yours you can still do it by editing the embed code - for example:
official embed code:
<iframe width="560" height="315"
src="https://www.youtube.com/embed/im-JM0f_J7s"
frameborder="0" allow="accelerometer; autoplay; encrypted-media; gyroscope;
picture-in-picture" allowfullscreen></iframe>
workaround solution:
<div onclick="this.nextElementSibling.style.display='block'; this.style.display='none'">
<img src="https://i.imgur.com/wEEFvCB.png" style="cursor:pointer" />
</div>
<div style="display:none">
paste embed code here
</div>
You can try it yourself here: https://www.w3schools.com/html/tryit
Or something more advanced like:
<div width="560px" height="315px" style="position: static; clear: both;
width: 560px; height: 315px;">
<div style="position: relative">
<img id="vidimg" width="560px" height="315px"
src="https://i.imgur.com/wEEFvCB.png" style="position: absolute;
top: 0; left: 0; cursor: pointer; pointer-events: none; z-index: 2;" />
<iframe id="unlocked-video" style="position: absolute; top: 0; left: 0; z-index: 1;"
src="https://www.youtube.com/embed/im-JM0f_J7s" width="560" height="315" frameborder="0"
allowfullscreen="allowfullscreen"></iframe>
</div>
</div>
<script type="application/javascript">
var monitor = setInterval(function(){
var elem = document.activeElement;
if(elem && elem.id == 'unlocked-video'){
document.getElementById('vidimg').style.display='none';
clearInterval(monitor);
}
}, 100);
</script>