My suspect is of course actual base64 data, otherwise it looks good to me. See this fiddle where similar scheme is working. You may try specifying char set.
<div>_x000D_
<p>Taken from wikpedia</p>_x000D_
<img src="data:image/png;base64, iVBORw0KGgoAAAANSUhEUgAAAAUA_x000D_
AAAFCAYAAACNbyblAAAAHElEQVQI12P4//8/w38GIAXDIBKE0DHxgljNBAAO_x000D_
9TXL0Y4OHwAAAABJRU5ErkJggg==" alt="Red dot" />_x000D_
</div>
_x000D_
You can try this base64 decoder to see if your base64 data is correct or not.