Instead of using image planes for reference pictures, how about creating a plane with your reference picture as a texture.......

Here's what I do:

If I am modelling in NURBS, I make a polygon plane (and vice versa if modelling in polygons) for each view and assign my reference picture to it as a texture.

If I don't want the reference planes showing in a particular view I can use the SHOW menu for that view and select what is shown and what is not.

I usually set the reference planes up in a separate layer as well, with the layer selected as a reference layer. This allows the reference picture planes to be shown but not accidentally selected.

Hope this helps

Steve