By banner, I presume you mean signature really. If you want to create your own one, it’s not down to creating an image file, like I’ve seen you’ve tried on another thread. You need to create it in BBCode. That is not trivial, and you need to invest quite a bit of time, but some of the basics are explained here:

How to make bitcointalk signatures [ Logo and Images included ]
How to Become Signature Master in 12 Hours. I did it, so can you
[LEARN] BBCode Lessons & Tutorials [+tutorial videos!]

You can get a rough idea by lowing at bounty threads, and seeing the signature structure they use, which is what people place in their signature. Not trivial to design, but there are some online tools that may help you (one of the above links reference a couple). There are also people here that can design a signature for you (check out the Services thread), if you need a good design but lack the time or knowledge on how to create one.