steelfeathers writes in her great
"All-Inclusive Guide to Texturing" :
http://www.minecraftforum.net/topic/659230-the-all-inclusive-guide-to-texturing/#biomeshading"How to make a banner
Create an image that represents your pack. Be sure that the name of your prack is clearly visible. The image must be no more than 100 pixels tall by 728 pixels wide!
Upload the image to the internet using an image hosting site, such as tinypic or imagur.
Copy the image URL the site gives you, and paste the image into your OP using the following code, which generates an image that people can click on to get to your pack:
[url="Your pack URL"][img]Image URL[/img][/url] "
it´s very easy! you can make one of your own! 
