The layout uses the system name stored with the emulator settings in Attract Mode. In order to show the banner that changes depending on the system, go to the emulator settings in Attract Mode and type in a system name. The layout uses the same system names that are used on the thegamesdb.net. Look in the banners subfolder of my layout if you are unsure about the system names to use.
For example, the system name for your Super Nintendo emulator should be called "Super Nintendo (SNES)." So go to your snes emulator in Attract Mode, and set the system string there to that exact string.
Note:
You can add your own banners by putting png files in the "banners" subfolder named [system]_banner1.png where [system] is the system name you configure in the emulator settings in Attract Mode. The banners look best if the aspect ratio is the same as 400*63 pixels and if there's a transparent color to allow blending with the background. I used paint.net and pictures of the consoles from Wikipedia to make some additional banners included with the layout.
Note: this feature makes use of the [System] magic token introduced in Attract Mode 1.6.2 so it will not work with older versions.