If you are looking for ready-made WinPE ISOs (with UEFI-boot support too), check out the Gandalf's WinPE builds of WinPESE8.1 (Google for 'Gandalf WinPE').
There is even a dual-boot x86/x64 ISO (64-bit UEFI + 32&64-bit MBR booting)...
Win8.1U1SE_x86 updateable (UEFI+MBR bootable) - This PE had external Portable Apps and Programs folder, allowing you to add more programs.
There is even a dual-boot x86/x64 ISO (64-bit UEFI + 32&64-bit MBR booting)...
The dual-PE ISO has an external Portable Apps folder, so you could add more apps into it.