Yes, it's true! You can make your very own skins for BoS.
Here's How:
1. Find your BoS Skin direcrory - "<<PATH TO BOS>>\skins"
2. Make a folder in your BoS Skin Directory with your skin's name - example: "C:\bos\skins\skin name"
3. Open that folder
4. Make a new text file called ClockFgColor.txt
   Open the file, and add a comma seperated color value on the first line
   (example: 0,100,0 would make dark green)
5. Make 4 more text files and edit them in the same way as above: 
   IconBGColor.txt
   IconFGColor.txt
   IconShadowColor.txt
   TaskbarFGColor.txt
6. Make the following images:
   DownArrowUp.bmp - The picture for the down arrow when it is not pressed - 20 X 30 Pixels 
   DownArrowDown.bmp - The picture for the down arrow when it's pressed - 20 X 30 Pixels 
   UpArrowUp.bmp - The picture for the up arrow when it is not pressed - 20 X 30 Pixels 
   UpArrowDown.bmp - The picture for the up arrow when it's pressed - 20 X 30 Pixels 
   ProgramNone.bmp - The picture for an empty program button on the taskbar - 250 X 30 Pixels
   ProgramUp.bmp - The picture for a normal (not selected) program button on the taskbar - 250 X 30 Pixels
   ProgramDown.bmp - The picture for a pressed (selected) button on the taskbar - 250 X 30 Pixels
   Seperator.bmp - The picture for a seperator (goes between the start button and programs) - 6 X 30 Pixels
   StartButtonUp.bmp - The picture for the start button when it's not being pushed - 60 X 30 Pixels
   StartButtonDown.bmp - The picture for the start button when it IS being pushed - 60 X 30 Pixels
   TaskbarBG.bmp - Picture to be streatched accross the taskbar for the background - 5 X 30 Pixels
   SystemTray.bmp - Background for the system tray - 100 X 30 Pixels
   PSCUp.bmp - The picture for the PSC "current code" button when it's not pressed - 25 X 30 Pixels
   PSCDown.bmp - The picture for the PSC "current code" button when it is pressed - 25 X 30 Pixels
7. Record the following sounds:
   hover.wav - The sound that is played when a button on the start menu is moved over
   open.wav - The sound that is played when the start button is pushed
   select.wav - The sound that is played when a button is pushed on the taskbar or start button
8. You're done! Email me at webmaster@pokecenter2000.com if you want your skin posted in the BoS online skin directory

If you need any examples, you can always look at the skins that come with BoS, Green Shades and Red Shades.