Spalted maple makes beautiful veneers. I have used it a bunch. Be careful grinding the veneers too thin though. They have a tendency to split when you apply pressure during the glue up. I even start with my air compressor off and let pressure build up slowly. My recommendation is to grind them to .03" or .025", but no less. Note: If they do split it does not cause a problem structurally. You will just see the core wood through the split. If you are using a maple core wood, any splits will hardly be visible.
--Mike