I had a moment to test the problem and had the same result with mental ray.
What I have to do is start with a new material, then apply the bitmap to the diffuse slot, apply this material to the object and this solves the problem.
Interesting, when I have a max file where the situation looks like in the picture:
Octane render is active and octane materials icons in the editor/prewiew window/material browser are not visible but standard materials icons are visible.
This is not an octane problem. This is a 3ds max problem, I think.
Thank you for your patience.