As far as I know, you have to build this with Blender

It is located at `\blender\blender\release\datafiles\splash.png`

Just replace<sup>1</sup> that one with one of the same size.

![enter image description here][1]

- <sup>1</sup>Here is a link to the entry on the [wiki][3] on how to correctly change it.
- You can grab an old [template][4] here which should still work and size your image accordingly ([src][5]).
- BlenderCookie has a [tutorial on building Blender][6] in which the author changes the splash screen. *(He uses mac but the majority of process can be done pretty much the same way for other platforms)*


  [1]: https://i.sstatic.net/5rwXI.png
  [3]: http://wiki.blender.org/index.php/Dev:2.4/Doc/How_to/Edit_the_SplashScreen
  [4]: http://download.blender.org/demo/test/splash_template_2.50.png
  [5]: http://blenderartists.org/forum/showthread.php?225288-Blender-2.59-splash-contest
  [6]: http://cgcookie.com/blender/2010/10/25/building-blender-in-osx/