Just a quick note that c:\Program Files\Windows Photo Viewer\ImagingDevices.exe uses LoadLibrary to load sti_ci.dll and as such it can be used to sideload any DLL.

All you have to do is copy ImagingDevices.exe over to a temporary folder, drop your DLL there as well, just make sure it is named sti_ci.dll, then run:

ImagingDevices.exe /InstallWiaDevice