Do you mean with in-game chat or on the forum?
All it takes is a quick search and you can find an image host, like TinyPic, where you can upload your image and stick it between two image tags.
[img]www.example.com/images/myphoto.png[/img]
For in-game images, it would be more appropriate to just post the link rather than force people to see it, especially as it could be offensive content.
Emotes don't seem like such a bad idea though.