Cool little skull I made for a cover art, I personally think it looks best clear, but clear shaders can be weird and awkward depending on the rendering environment, ( I used Blender Eevee renderer for the effect for example ) so it might be a good idea to play around with it a bit if you intend on using it in another renderer or game environment, I'll include a .glb and .obj / .mtl for ease of use, but I've been testing the .glb format a lot and they seem to carry the shader information correctly ( at least in blender ) so I think that one should be good enough ( obj is basically just for easy access if you wanted to render it seperately with your own shaders and whatnot, rather than using the glass transparent one I set up specifically in blender. )

That should cover about everything, I'm more of a sculpter / modeler than a manager of textures and shaders lol so hopefully everything works well in your environment! :)

( The skybox isn't included of course, its just to show off the shader effect of the glass skull, which is pretty much invisible without surrounding objects and textures. )