Combining a background style with another background image

Molly If I understand you correctly the logo is in the background of the slide and you can't separate it from the background style.

Go in and amend the slide master by going to view- master slide master and in the main presentation select all objects.

To select all objects go to the Edit menu and choose select all

From the drawing toolbar which is normally at the bottom of the screen select Draw and select Ungroup.

This should detach the logo from the background image and you should be able to manipulate it.

Ctrl+Click to select all other objects apart from the logo to regroup them.

Remain in slide master view and select the logo and apply the custom animation you require.

Hope that helps. If not please upload a slide for us to examine.

Thanks