I don't see why not on the 32-bit version.

This is just a quick hack fix for folks who want a theme they use most of the time.
This isn't a permanent fix by any means as it does allow you to use a similar theme color set with smaller icons but you are stuck with that theme color set until you change the gtkrc file in the UserFolder/.gimp-2.8 folder again!

The Hack-
I simply copied the Aurora Midnight gtkrc theme file and pasted it into my UserFolder\.gimp-2.8 folder
I overwrote the existing gtkrc file. On Gimp restart the icons should already be small but if not...
go to Edit>Preferences>Themes and select small.

The smaller icon code is written into the Aurora Midnight gtkrc file already so once you switch to Edit>Preferences>Themes>Small , the file finds the smaller image code automatically.
If you switch back to default the larger icons return.

Yes mathmap can be added.
mathmap.exe in the plugins folder and mathmap expression folder in the UserFolder\.gimp-2.8 folder.
Restart Gimp-2.8