@Christian: I'm sorry. I'm fighting with it for more then hour. "Fortunately" on my device with Android 4.0.4 it do exactly same problem. No matter what I do, result is always only black image with blue thin border. Android completely ignores my attempts to render whole screen into simple image. From what I was able to find about similar problems, it looks like generated preview is too big on this Android version. So I'll have to disable this feature for all 4.0, 4.1 Android versions, sorry.
@HtV: ah perfect, I got it! You tap twice on back arrow, so it returns you to root menu of "Map content" panel, not just to list of map themes. Perfect, thank you, issue fixed!