You just post an image with the number that proceeds from the previous post.
Sample:
Post #1:
[quote] [img]http://farm1.static.flickr.com/39/120450736_05c7130959.jpg[/img] [/quote]
Post #2:
[quote] [img]http://idn.efashionsolutions.com/asset/image/format/NE-ex/id/NE-BUFFFOOTSU09920_12_royalwhite_front[/img][/quote]
[img]http://upload.wikimedia.org/wikipedia/commons/thumb/d/dd/California_1.svg/385px-California_1.svg.png[/img]
weird ones are worth it.
[img]http://www.boston.com/travel/blog/super8.jpg[/img]
There was a photo of an octobaby but I decided to choose a less terrifying photo.
What the hell here it is in tags. NSFW
[url]http://media1.break.com/dnet/media/2008/7/21july5-8-legged-baby-growing-up.jpg[/url]