If your looking for gimp brushes to download i know just the places.
first of all you if you don't know how to install them here is a quick guide on how to get those brushes installed in Gimp.
How to install Gimp Brushes.
To make a brush available, place it in one of the folders in GIMP's brush search path. By default, the brush search path includes two folders, the system brushes folder, which you should not use or alter, and the brushes folder inside your personal GIMP directory. You can add new folders to the brush search path using the Brush Folders page of the Preferences dialog. Any GBR, GIH, or VBR file included in a folder in the brush search path will show up in the Brushes dialog the next time you start GIMP, or as soon as you press the Refresh button in the Brushes dialog.
now that you know how to install them here is a few places to get some of those brushes
Gimp brushes from gimp-tutorials.net
deviantart.com
