I was struggling a lot to fine full-Markdown library that it's easy to use and finally I found CocoaMarkdown.
It's really great, supports most of the syntax and have easy to use API. The only thing that was missing was image support, so I forked it and add full-image support, along with cacheing and enabling to use images wrapped in URLs, hope it will solve the problem I had for someone else:
https://github.com/X8/CocoaMarkdown
