There are multiple ways of viewing BART datasets and images. If you are using the Matlab interface, A Matlab-based image viewer which works well with BART is arrayShow by Tilman Sumpf.
If you have Python installed, you can view BART datasets using the bartview.py script in the folder python to view the images. The simplest way to use it is to install python through Anaconda. To use the script to view a dataset img (with files img.cfl and img.hdr), type the following in the command line:
$ python bartview.py img