The gltf model model file loading can sometimes show that the texture can not be displayed at some time, and sometimes there is no texture. I don’t know what cause.
floor.gltf (4.97 MB)
I responded to your other post here: https://groups.google.com/forum/#!topic/cesium-dev/fLJPg7k8Dt0, but I think I found the actual reason why it’s failing.
One of the images in the glTF has a mime type data:image/x-tga which suggests it is a TARGA image. If you convert this image to a png or jpeg instead the model should load fine.