I have a fix. But I couldn't test it. I had trouble setting up the build 
environment.
Can someone test it for me, please?

The fix is here: 
https://code.google.com/r/marioweber88-vim/source/detail?r=ed13ee673efda7fdacf0c
db53e98bd6b97b30ee5

Thanks for stepping forward and making those changes. For building Vim with 
Windows, see this wiki entry: 
http://vim.wikia.com/wiki/Build_Vim_in_Windows_with_Visual_Studio

Note those changes need WINVER=0x0500 so you need to adjust the Makefile and 
have APPVER=5.0 then you can successfully build it.

I compiled it and installed it manually as described in the readme (e.g. copied 
the dll to c:\windows\system32, merged the reg file, changed the path in the 
registry to point to the actual gvim.exe binary and right clicked on a file. 
Unfortunately, there was no icon in the popup menu. 

So could you please have another look? Thanks.

I'll look at it again.

I'm using Windows 8.1 64-bit and VS2013.

I couldn't build with the makefile at all. I got an error for a missing file.

So I created a new project in VS and copied the source files. I had to make 
some more changes, because the variable oldenv was not defined. I didn't commit 
those changes, because I thought this error was due to my build setup being 
wrong.

But using this I could compile and I saw the icons in the context menu. Only 
problem was an error message when I selected an entry. I think this was because 
of the oldenv problem I didn't use unicode when creating the process for vim.

Think I fixed it =)

https://code.google.com/r/marioweber88-vim/source/detail?r=b3ed4ffac395f73e2e693
6a3b51be132f669ba14#

Works fine on my system.
Let me know if it works for you too.

Works fine now. 

Only needed to change APPVER to 5.0 in Makefile, as described above, when 
compiled with MSVC compiler. And also add -lgdi32 to LIBS in Make_ming when 
compiled with MinGW (MinGW64 in my case).

fixed in 7.4.724