As you probably know, WDS doesn't provide any security for it's native boot images (Windows PE 2.x). However, by adding pxelinux and vesamenu.c32 to WDS, you can add that feature. Here is how...

1. Download and extract syslinux from http://www.kernel.org/pub/linux/utils/boot/syslinux/syslinux-3.71.zip (it contains pxelinux) 
    
2. Copy the syslinux-3.71\com32\menu\vesamenu.c32 to your WDS Server, D:\RemoteInstall\Boot\x64 and D:\RemoteInstall\Boot\x86 
    
3. Copy the syslinux-3.71\core\pxelinux.o to your WDS Server, D:\RemoteInstall\Boot\x64 and D:\RemoteInstall\Boot\x86, rename it to pxelinux.com 
    
4. Download a nice background image (http://www.deployvista.com/Portals/0/DeploymentBackground.png), and save it in D:\RemoteInstall\Boot\x64 and D:\RemoteInstall\Boot\x86  
    
5. In the D:\RemoteInstall\Boot\x64 and D:\RemoteInstall\Boot\x86 folders, make a copy of pxeboot.n12 and rename it to pxeboot.0 
    
6. Configure WDS to use the pxelinux.com boot file (Server properties, Boot tab) 
    
7. In the D:\RemoteInstall\Boot\x64 and D:\RemoteInstall\Boot\x86 folders, create a subfolder called pxelinux.cfg 
    
8. In the D:\RemoteInstall\Boot\x64\pxelinux.cfg and D:\RemoteInstall\Boot\x86\pxelinux.cfg folders, create a file named default with the following settings
    
   DEFAULT      vesamenu.c32
   PROMPT       0
   NOESCAPE     0
   ALLOWOPTIONS 0
   # Timeout in units of 1/10 s
   TIMEOUT 300
   MENU WIDTH 40
   MENU MARGIN 0
   MENU ROWS 12
   MENU TIMEOUTROW 14
   MENU HSHIFT 5
   MENU VSHIFT 2
   MENU COLOR BORDER 30;44       #00000000 #00000000 none
   MENU COLOR TABMSG 1;36;44     #00000000 #00000000 none
   MENU COLOR TITLE 1;36;44     #00000000 #00000000 none
   MENU COLOR SEL   30;47       #40000000 #20ffffff
   MENU BACKGROUND DeploymentBackground.png
   
   MENU TITLE PXE Boot menu
   MENU WIDTH 80
   MENU MARGIN 18
   MENU ROWS 4
   
   LABEL wds
    MENU       DEFAULT
    MENU PASSWD P@ssw0rd
    MENU       LABEL Windows Deployment Services
    KERNEL     pxeboot.0
   
   LABEL local
    MENU LABEL Boot from Harddisk
    LOCALBOOT 0