Below are some quick-and-dirty brain outline images I’m using in a talk I’m giving in a couple of weeks. I like the calligraphic quality that the axial and sagittal slices have. The coronal image is a little more colouring-book in its outline.

axial outline
sagittal outline
coronal outline

They’re very easily generated with screengrabs from MRIcron that are processed in GIMP with a straightforward series of the following steps:

1) Edge-detect
2) Invert Colours
3) Gaussian Blur
4) Brightness-Contrast

Repeating steps 3 and 4 a couple of times will get the consistency of line seen in the coronal image.