examples:
I stand corrected regarding the width and height specifications. Markdown usually allows it but Steemit doesn't seem to
Markdown

Result
Markdown
<img src="http://i.imgur.com/bmQVfyB.png">
Result
Markdown
<img src="http://i.imgur.com/bmQVfyB.png" width="50px">
Result
Markdown
http://i.imgur.com/bmQVfyB.png
Result