These files are used by anaconda during the installation process.  A
basic description/specification for them is as follows:

* anaconda_header.png:  This is strip header at the top of
  the screen during the install. 800x58.
* progress_first.png: First graphic displayed during package
  installation.  If there are no rnotes, this is displayed the entire
  time.  500x325
* progress_first-lowres.png: Lowres version of progress_first.png. 350x225
* splash.png: Splash screen shown on the "Welcome to ..." screen.
  400x420
* syslinux-splash.png: Splash screen used at the boot prompt with
  syslinux/isolinux.  This gets transformed into the syslinux specific
  format.  640x300.  This uses a 16 color palette (should be an indexed png).
  You should ensure that 0 = #000000, 1 = #ffffff, 7 = #cdcfd5, 15 = #c90000.
  Alternately, you can use 12 colors and have them be any that you want.
* syslinux-vesa-splash.jpg: Splash screen used at the boot prompt when
  using the menu.  It should be 640x480 RGB.  Can just be a conversion
  of the grub splash and work well.