Well, I use Adobe Photoshop to make them. I find it's the best graphics program there is, and it's the industry standard. A similar program would work well, such as the latest version of Paint Shop Pro. You might find a free version at
www.tucows.com.
Pictures can be found all over the web, they aren't exactly hiding anywehere.
*Shrugs* I guess nobody wants banners from me.
