Ok, I've just tested this with the Windows built in Photos app on Windows 8.1 x64, and injection works just fine with the HookProcessCreation demo, after I've added "ALL APPLICATION PACKAGES" NTFS read/execute rights:
http://madshi.net/HookProcessCreation.zipThe PrintMonitor didn't work because it only injected in the current user session, while apps seem to run in a different session. If you switch the HookProcessCreation demo into "system wide" mode, it works with the Photos app, at least.