You haven’t really said what you have done, so it’s hard to say what you might be doing wrong.
Are all of your display objects sprites? If so, do any of them have invalid frame references? Do you insert everything properly into groups? Really, we are just going down the checklist of how you are creating your display objects.
If you create only the background and nothing else, does it work then? If so, then probably your display groups (or inserts into them) aren’t correct. If you don’t see the background and it is a sprite, ensure that the frame index is correct and that you haven’t accidentally altered the object’s alpha or scale values (and that the object is actually on screen). If you’ve created those image sheets by yourself, then there may be problems there as well.