Indeed, setting it up as a panel is the usual test to check whether a bitmap is correctly written. If it's visible in a panel, it also looks the same when you use it as a model or terrain texture.

So the problem is somewhere else, like using the wrong bitmap for your effect. Another possibility is when the bitmap is converted to a normal map or uv map etc, which of course alters it totally.

Saving a bitmap is implemented in the beta version and is in experimental state currently.