Thanks for posting this Batarzell. I tried it and had a couple of observations. It did work OK, but it didn't seem to do a very good job of setting up shortcuts, and it didn't provide any way to uninstall the package (apart from just deleting the files in c:\program files\synfig)
The good news is that it prompted me to dig into this for myself. I took a different approach and started from the build tree and the current core and studio NSIS install scripts. I combined them and added in the GTK/GTKmm files. The result is the latest version from the Git repository, compiled with GTK version 2.16.
You can find my version at viewtopic.php?f=1&t=740
Please give it a try and let me know what you think.