GJCR is a quick graphic tool to view JCR5 and JCR6 files... It is also able to handle WAD (Where's all the Data?) files, as used in DOOM, Heretic, HeXeN and Rise of the Triad, and the PAK files used for Quake (at least Quake 1 as I do not know if later instalments use the same system) :)
More details are described on the [https://github.com/Tricky1975/GJCR_Sharp/wiki](wiki page).