If you just want a Tardis, check out the thing I derived this from. If you want a Tardis with a hole in the top for an LED and plenty of room for batteries and electronics, this is it!
This is like 98% Gossamer's work, but I needed to modify it a little to get a 5mm LED to fit nicely in the top. I also changed the hollowed-out section in the middle to a square instead of a circle. This leaves plenty of room for a battery to power the LED. Instead of a dome at the top of the hollowed section, I used a 4 sided pyramid subroutine taken from randyy's OpenSCAD Parts Library. http://www.thingiverse.com/thing:6021
The only new feature that isn't parametric in this design is the diameter of the recessed hole meant to catch the LED's flange if it has one. This is permanently set to one, but feel free to change it or remove that line of code altogether if you don't want it.
I finally got the overhang right. It's parametric now, too. Go ahead and check out the instructions if you're interested.
I updated the scad file to have a parametric overhang slope for the hollow section. I currently have it set to tan(30) which works fine for me, but you may want to modify it if your printer is really good or really bad at overhangs.
You may also want to change the height. The stl is about 97mm high, which can be problematic for a prusa depending on your setup. Don't scale the print with your slicing program, because it will also resize your LED hole, which is the defining feature of this print! :)