Support for NiPalette node
NIF format allows to embed textures to meshes via NiPixelData load, and basically OpenMW support it via osg::Image, but only for NIPXFMT_RGB8 and NIPXFMT_RGBA8 formats.
If the NiPixelData is a palette image, the mesh just will not load because OpenMW can not read the NiPalette node.
Since osg::Image does not support palettes, a proper solution would be to read palette and convert such texture to a common RGB image on the fly and assign it to the osg::Image.