Little known secret about Pidgin that I can’t seem to find anywhere but that I somehow figured out.

Obviously it uses GTK for it’s window engine.  Logic tells us that it would use GTK themes in the same way.  This is correct.

You can grab your themes from Gnome-Look (only from the GTK 2.x category) and then extract them.

One you have your files, grab the folder that contains a folder with the name “gtk-2.0″ (id est, you would find the “gtk-2.0″ folder then hit “go up one level” one time, and then take that folder) and put it under C:\Program Files\Common Files\GTK\2.0\share\themes or C:\Program Files (x86)\Common Files\GTK\2.0\share\themes if you’re on 64-bit Windows.

This is the default location of GTK, if you installed it to a different you’ll need to go under /Share/themes from the root GTK install directory.

Then go to your start menu, find the GTK+ folder and launch “Theme Selector”, select the theme you chose from the “Global” list, hit ok, and now restart any GTK applications (like Pidgin).  You should have your new theme.