My suspect is of course the actual Base64 data. Otherwise it looks good to me. See this fiddle where a similar scheme is working. You may try specifying the character set.
<div> <p>Taken from wikpedia</p> <img src="data:image/png;base64, iVBORw0KGgoAAAANSUhEUgAAAAUA AAAFCAYAAACNbyblAAAAHElEQVQI12P4//8/w38GIAXDIBKE0DHxgljNBAAO 9TXL0Y4OHwAAAABJRU5ErkJggg==" alt="Red dot" /> </div>
You can try this Base64 decoder to see if your Base64 data is correct or not.