As D13 said, by default GameGuru only renders textures to the front face of a plane, if you created the walls using a single plane instead of a face for each side then you won't see textures on both sides, ideally you need to create an inside face for your wall to be visible inside and out. There is a way to force GameGuru to view the texture on two sides of a face, but I can't for the life of me remember how, it involves editing files so I never bothered with it.
i5, NV960 2GB, 16GB memory, 2x 2TB Hybrid, Win10.
i3 , Intel integrated graphics, 6GB memory, 512GB Generic SATAIII Win8.1.
Intel Celeron (duel Core), Radeon integrated graphics, 4GB memory, 180gB Generic SATAII, WinVista.
Q6600, Intel integrated graphics, 8GB memory, 512GB Generic SATAII, Win7.
