I must be doing something wrong ...
Thought I'd try importing a background and rendering the scene with the background - which works fine.
But when I come to export the rendered image there's no background.
Have I overlooked something?

When you render you need to check if "render over"  is set to background picture.

Exporting as png dont export background, try to export as jpeg .

Render over background is checked - so it's the png format that's the problem. Strange.
Thanks.

It is not a strange feature; it is easier to bring a render into a 2D program for postwork or a change of background. 

Thanks.

Quote - It is not a strange feature; it is easier to bring a render into a 2D program for postwork or a change of background. 

Maybe so but then if you wanted to do that then you can just render without the background in the first place. Also, the other export formats do save with the background...

I had the same problem no matter if render over background is checked. It seems that there are some bugs with Poser renders. Try to change display settings for Preview mode from OpenGL to Sree3d. Do simple render. Than change to FireFly. It won't always work. I haven't found the right reason why is this happening.

From my experience, you have to restart Poser from time to time. When it can't  export background picture, no matter if you have specified in render options to do so, try to do so with preview render by changing some render options. When you succeed with that switch to FireFly and save your presets. Remember that there can be a huge bug concerning Export and Render, depending on what options you use. Also there is a huge memory leak and Poser can often crash, and so this might be also a reason why it sometimes messes with renders.

The same thing above works also for issue when Poser doesn't export images as 32 bit depth PNG slides, but 24 bit instead. Then instead of transparent background you get gray background color.

REMEMBER also that what you get by rendering 1 image in Poser ( by pressing render button in upper right corner of the screen) is not always what you will get when exporting animation as PNG slides. It's quite frustrating, I know, but you have to be patient and try to figure out what options you should use when Exporting slides.

Sometimes unchecking 2d and 3d motion blur option is enough to fix this problem. Why? I have no idea. I hope that in new version of program they will fix this issue, since this Poser8 is most unstable version. Although PoserPro have also this issue, but P8 have much better render.

I don't mean to offend, but the funny thing is that people in my country who are not familiar with this Software often laugh when I mention it. The thing is that in Serbian, word Poser in slang language means something like "Shiter" or "Shit-boy". Other interpretation is "someone who got lucky" depending on how you use this word...

So when I work in Poser and after a good torture with exporting issues, when I finally got lucky and get what I wanted I always yell POSER!

Maybe there is something more in that? :)