I analyzed it in another comment: the header says the image is 300x300px 8-bit RGBA but the data is invalid. Most viewers will notice that and show an error.

However, the syntax it used for embedding images is valid, as data:image/png;base64, is the start of a valid image URL and you can use it like other image URLs in supported Markdown interpretors.

Example, using the 103-byte Google Maps' sea tiles, and a 178-byte GIF:

![Google Maps sea map tile](data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAQAAAAEAAQMAAABmvDolAAAAA1BMVEW10NBjBBbqAAAAH0lEQVRoge3BAQ0AAADCoPdPbQ43oAAAAAAAAAAAvg0hAAABmmDh1QAAAABJRU5ErkJggg==)
![wink.gif](data:image/gif;base64,R0lGODlhDwAVAKIEAAAAAP//AP//3v///wAAAAAAAAAAAAAAACH/C05FVFNDQVBFMi4wAwEAAAAh+QQFlgAEACwAAAAADwAVAAADSUiq0L2QtEDpg6Bqu/LeAGN5wVRKlVmS6qe17hiDHvlyNciho5N2sxDGtoIMBgyH8Kg4IiMEZ1NKlUarSOdTe81arZHvE3olJAAAIfkEBR4ABAAsCAAEAAQABQAAAwYIGtz+ASQAOw==)

renders as

Works in the default web interface