By Forrest Smith - Drempd.com
.ipad,.mobile{display:none;}
@media(max-width: 768px){
.desktop,.mobile{
display:none;
}
.ipad{
display:block;
}
}
@media(max-width: 500px){
.desktop,.ipad{
display:none;
}
.mobile{
display:block;
}
}
<img src="image-file-desktop" class="desktop">
<img src="image-file-ipad" class="ipad">
<img src="image-file-mobile" class="mobile">