Sorry about going quiet. I went to bed because I was exhausted. So I'm a massive noob when it comes to Photoshop as well, but I do know my way around some of its basic tools. My general process is as follows:
1. Make a thin black border. There's a few ways to do this, such as using the shape tool to draw rectangles, but the way I prefer to do it is by highlighting the area that I want to be the banner itself, then inverting the selection (Select -> Inverse) so that you end up with a kind of donut shaped highlight around the edge of your picture. From there, make a solid black adjustment layer. In my version when you make a solid color adjustment layer, it automatically cuts it to fit your selection, so it gives you a quick and nifty black border.
2. Find a background. For each different battle, I pick a different texture from this kind artist on dA who offers completely unrestricted use of their textures. From there I crop a piece out of the texture that matches the dimensions of the banner and paste it on a new layer behind the border.
3. Next is the text, something which you should probably play around with yourself. Some tips though; for ease of editing so that you don't have to move around text constantly whenever you edit what it says, you should justify your text to fit where it is in the image. If the text is in the center of the image, justify your text center. If it's on the left, justify it left, and so on. This will allow you to edit it quickly and easily later if you need to do something like change a name or increase the round number written on it.