Uma simples animação para aguardar o carregamento de imagens.

animation.html

<style>
    @keyframes change {
        from {background-color: #eee;}
        to {background-color: #f4f4f4;}
    }
    .img {
        position: relative;
        border: solid 2px #ddd;
        width: 300px;
        height: 300px;
        animation: change 0.5s infinite alternate;
    }
    .img span {
        position: absolute;
        top: 50%;
        left: 50%;
        transform: translate(-50%, -50%);
        font-family: Georgia, serif;
        font-weight: bold;
        color: #333;
    }
</style>

<div class="img">
    <span>Carregando...</span>
</div>