I posted a tutorial on making glowing runes with GIMP on the Dundjinni forums and thought I would point it out to any here that want to try their hand at GIMP.
Tutorial on Dundjinni forums
Here's what the end result looks like in Dundjinni (and thus more or less what it would look like in MapTool).
I also posted 80 or so alchemical symbols done in the same fashion to a thread there as well.
Alchemical Symbols
Look near the bottom of the page linked above and then on the next page.
Making Glowing Runes with GIMP
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