I'd go for a flexbox:
<style>
#slide {
align-items: center;
display: flex;
flex-direction: column;
}
#slide > img {
max-height: 300px;
}
#slide > p {
font-size: 300%;
margin-top: 0;
}
</style>
<div id="slide">
<img src="upload.wikimedia.org/wikipedia/commons/7/73/Lion_…">
<p>Der Löwe</p>
</div>