This smile theme will replace your existing smiles with rage faces from reddit.com. The package includes instructions, but it's fairly simple. Decompress archive to %APPDATA%\.purple\smileys (if you're using Windows) or ~/.purple/smileys (if you're using Linux/*nix). You may have to restart Pidgin if this is the first time you have installed it.
Don't have Pidgin? Get it here.
All of the files for the Rage Face theme are now hosted on github.