I added if(newVal >= 0 && newVal < 35)
with 2 conditions to check if value is in a range and then set <img>
You can't use document.getElementById("img").src = newVal+ ".jpg";
, in that case you will get 100 different images
<input id="valR" type="range" min="0" max="100" value="0" step="5" oninput="showVal(this.value)" onchange="showVal(this.value)" />
<span id="range">0</span>
<img id="img">
<script>
var val = document.getElementById("valR").value;
document.getElementById("range").innerHTML=val;
document.getElementById("img").src = val + ".jpg";
function showVal(newVal){
document.getElementById("range").innerHTML=newVal;
if(newVal >= 0 && newVal < 35)
document.getElementById("img").src = "first_image.jpg";
else if(newVal >= 35 && newVal < 65)
document.getElementById("img").src = "second_image.png";
else if(newVal >= 35 && newVal < 65)
document.getElementById("img").src = "third_image.png";
}
</script>