Placeholder background/image while waiting for full image to load?

Instead of referencing the image directly, stick it within a DIV, like the following:

<div class="placeholder">
    <div class="myimage" style="background-image: url({somedynamicimageurl})"><img /></div>
</div>

Then in your CSS:

.placeholder {
    width: 300;
    height: 300;
    background-repeat: no-repeat;
    background-size: contain;
    background-image: url('my_placeholder.png');
}