What is .GBR file?
Image brush used by the GNU Image Manipulation Program (GIMP), an open source image editing application; stores the description, bitmap image, and the spacing for the brush; used for storing graphics that can be repeatedly painted on a GIMP image canvas.
GBR files are used to store both the default program brushes as well as custom user brushes. Some default brushes are located in the /share/gimp/2.0/brushes/ directory of a GIMP installation.
Recommended Software Programs to open .GBR file