Brick.ie The Irish Association for Adult Fans of LEGO®

The easiest way to post pictures of your MOC is by putting them on Flickr. Flickr gives you free image hosting and as a bonus there's a lively LEGO community in various groups.
Sign up for a Yahoo account: https://login.yahoo.com/account/create
Then start uploading on https://www.flickr.com

Once your picture is there, it is easy to share:

Flickr - BBCode link by Duq, on Flickr

Click on the share (arrow) icon, then select 'BBCode', pick a width around 640px and copy the bit of code that's highlighted. You paste that code in your post and that's all there is to it.

If you have a picture on some other image hosting site you can still insert it into your post using the [img] and [url] tags:
[url=http://url.to.your.image.page][img]http://url.to.your.image[/img][/url]
Again, use an image up to 640 wide to put in the post, you can link to the large version.

So this:
[url=http://www.brickshelf.com/cgi-bin/gallery.cgi?f=80863][img]http://www.brickshelf.com/gallery/Duq/Animation/v8_2.gif[/img][/url]
Will do this: