Based on the code here, http://developer.android.com/guide/topics/ui/dialogs.html#CustomDialog . I am successfully able to create a custom dialog with background and buttons ins
Try the following style in your styles.xml:
For more options see "Theme.Holo.Light.Dialog" which is part of the Android sources (since Honeycomb), or any other dialog style you based your's on.
Then simply use this style as basis to your own dialog:
Dialog myDialog = new Dialog(getActivity(), R.style.free_floating_dialog);
myDialog.setContentView(R.layout.myContent);