On the client MC, use handheld settings in options to set a local folder as a handheld device... "Options > Handheld > add device"
Set image conversion options to none for this new device.
Connect to MC server, in the action window, select Handheld, pick the one that is the local folder, drag image files to the now present sync list window in the action window, and when you hit "Sync" the images will be copied from the server MC to the local folder on the machine of the client MC.
The client has to pull them, the server cannot push them.
You could try using a smartlist to sync with on the client MC, then, all you would need to do at the server end is ensure that a tag, or tags, are set that you know will mean that that image will be included in the client sync list because it now satisfies the rules you set in the client sync rules smartlist (on the client).
I'm currently messing around with Google and iCloud photos.
By using their desktop apps, any photo taken on my phone is automatically imported into MC minutes later.
iCloud has a sharing folder. Any photo I add into a given 'shared' folder automatically appears on the device of the person or persons shared with, including, presumably, their desktops if they also have the iCloud app installed?
Dropbox also does shared folders and a desktop app. I know you said you wanted to avoid the cloud services, but really, this is what they were designed for, and you can easily incorporate the sharing workflow into MC at your end, making the 'shared with' end of the line much easier than this MC client/server/handheld cludge, which relies on the server MC always being available whenever those remote clients need it, while cloud services do not.
Happy Christmas,
-marko