(also, the pedant in me would like to point out that this is not "shell scripting" as you're not scripting a shell, but it's super cool regardless)
I'm starting to use Go for these sorts of things because it's really fast. I'd try objc but if I want to move my programs to a Linux server, I'm out of luck.
But I wanted libdispatch, blocks, all the stuff in the newer objc runtime, etc. Back then that meant playing all sorts of games compiling a specific objc runtime (there's more than one outside of apple), in a specific order with other things from GNUstep, using clang at certain steps instead of gcc to compile it all. It was a mess, but if I had really wanted to I probably could have pulled it off, and now I'm sure things have improved. I moved the entire thing to python and forgot about it though.
But I've always liked the idea of writing little things that have no GUI of any kind in objc, I wrote a few commandline utilities in objc and loved it. Background services on the system (mac or linux either one) would be fun too I think.
In this case, the GP is correct: NSImage is part of the UI toolkit (AppKit); it is not a core API exposed by, say, Foundation.