FlexImg

HTML

<div>
    <img src="http://loremflickr.com/100/100" />
    <img src="http://loremflickr.com/100/100" />
</div>

CSS

div
{
    /* size */
    width: 100%;
    height: 300px;
    /* flex */
    display: flex;
    align-items: center;
    justify-content: center;
    /* look */
    border: 1px solid #666;
}

div img {
    margin: 0 5px;
}