One of the newer updates to Pidgin made it a little harder to use GTK+ themes in the application (I like mine to look like the window below). You can follow the instructions from this link to get Pidgin looking decent:
http://developer.pidgin.im/wiki/Using%20Pidgin#win32_gtk_theme
Once you’ve modified your Pidgin install, you will want to place your themes into <Pidgin Installation Directory>\Gtk\share\themes. My favorite Pidgin/GTK theme is ClearLooks DarkLime. It’s awesome for both Pidgin and Ubuntu.

Author: FredLL1950
November 22nd, 2011
at 1:26 pm
Thank you so much for this! I was all over the web looking for how to use themes in Pidgin & it seemed no one could do it in plain English until I found this page through Google. You are the only one I found that explained it in a way that was easy to understand.