You will want to save your contrast image in NIfTI format, and then you can load the image just like a statistical map. For example here

http://brainmap.org/software.html#Sleuth

Once you create the NIfTI image "MyMap.nii" you could visualize it, for example the MRIcroGL script:

import gl
gl.resetdefaults()
gl.loadimage('spm152')
gl.overlayload('myMap')