All the settings are in a single file. Look for the file igconfig.xml - this should be in in the same folder as ImageGlass.exe, assuming you're using the 'portable' configuration.
You can copy igconfig.xml to any other computer where ImageGlass is to be installed - copy it to the ImageGlass.exe folder on every target computer.
There is one known problem - the "Theme" setting uses a path which will (likely) be specific to every computer. I'd suggest deleting that line from the igconfig.xml file before copying it - you will then need to using the Settings dialog to configure the Theme.
The line will read:
<Item key="Theme" value="(path to config.xml)" />
I hope this helps,
Kevin