If you do like what someone puts up, please save the picture to your own image hosting site. The reason I say this is because everytime you link the url or use the image, you're taking their bandwith and you only get so much bandwith.
If you don't know how, it's very simple.
1) Right-click on the image.
2) Save the image onto your computer.
3) Find an Image Hosting Website such as: Photobucket.
4) Upload the image.
5) Then use this code except change the url:
[IMG]www.yoururlhere.com[/IMG]
If you would like to add a url into the image use this code:
[url=http://www.yoururlhere.com][img]http://www.yoururlhere.com[/img][/url]