Unless there is clearly a problem (ie: the officer gets suprised thinking you are a motorcycle because he couldn't see one of the lights), it is unlikely you will get pulled over for it. My experience is most want cut and dry tickets to issue if there is no incident already.
The vehicle code in most states (probably all) does require headlights and there is the implication they should not be obstructed so in theory they could issue you a ticket.
The most likely scenario where you could get in trouble is if you have a crash at night and someone brings up the bikes blocking the headlights.