[3dtrialpractice]

Yes open it in your Beat Maxwell image viewer, or the viewr that pops up when you render with Mx~Render. File>Load image (loads your jpeg) give the image an Emmission intensity in the viewer Image/MXI controls .
File>save MXi

In maya creat an mxEmitter node, in its attributes, goto extra attributes flipdown and then TYPE the FULL PATH of your .MXI texture into the Mxi Map field.

Hope this helps.
(best maps ar masked off in photoshop just to expose the lightsources of the image)

HERE'S a Wonderful example! from this thread:

http://www.maxwellrender.com/forum/viewtopic.php?t=3640

Testing emitter MXI