Hi Mike, can I assume you have enabled the old Photo Viewer in Windows 10 via the registry?
Yo can add that on the right click context menu of image files as follows:
Click your Start Button, type regedit and hit Enter
In the left pane, navigate to:
HKEY_CLASSES_ROOT\SystemFileAssociations\image\shell
Create a new key under shell key and set its name to any desired string such as openwpv
Create a new key under openwpv key and set its name as command
In right-side pane, double-click on Default
Set its value to (copy and paste):
%SystemRoot%\System32\rundll32.exe "%ProgramFiles%\Windows Photo Viewer\PhotoViewer.dll", ImageView_Fullscreen %1
In the left pane, create one more new key under openwpv key and set its name to DropTarget
Click DropTarget and in right-side pane, create new string CLSID and set its value to {FFE2A43C-56B9-4bf5-9A79-CC6D4285608A}
That's It, now Photo Viewer will appear in the right click menu of File Explorer