There are two distinct splash sections.
The ISO has a splash section, specified by a message file, and used by /isolinux/isolinux.bin.
The Linux kernel has its splash section. This section specifies the Linux kernel's splash screen.
Should you choose not to have a kernel splash, select no from the Splash option list.
You can specify the resolution in the situations where a boot theme has more than one resolution.
Create Theme will start the DrakSplash program. This is an excellent program to create extra boot themes with.
Use Defaults / Refresh can be used to fetch the latest list of available boot themes.