1. Take full image link
Code:
http://uploadffs.nl/images/wow201oso.png
2. Replace "images" with "thumbs"
Code:
http://uploadffs.nl/thumbs/wow201oso.png
3. Add [img] tags
Code:
[img]http://uploadffs.nl/thumbs/wow201oso.png[/img]
4. Add [url=full link] tags
Code:
[url=http://uploadffs.nl/images/wow201oso.png][img]http://uploadffs.nl/thumbs/wow201oso.png[/img][/url]
5. Done


Thanks to whoever I stole that example picture from.