Cut them up in PS or whatever you use. Then open Maya. Choose the view you want the plane in and go View > Select Camera, then press Ctrl + A to open the attributes editor, scroll down to "Environments" and expand that tab. Click create image plane, then just choose your image.

I think that's right anway.

Also if it's slowing you down alot go back the the image plane attributes and change the display mode to RGB not RGBA as you don't need and alpha channel and change "all views" to "look through selected"