I'm guessing the league and teams have teams of people looking at this, but there are ways to make the home viewing experience closer to what it was. Some of these like crowd noise could also help the players adjust to playing in an empty stadium.
Low tech - Instead of leaving the empty seats uncovered - tarp the entire lower deck with home team colors and logos to fill the backgrounds of shots. Some of the poor selling home teams (jaguars) have been doing this for years for the upper deck.
High tech - take some sample crowd shots from recent games and digitally replicate them and add them in the background. You can even put them slightly out of focus. It's how a lot of movie crowd shots are done, also the armies of Orcs in lord of the rings.
Sound - the league could sample a series of crowd decibel levels across stadiums the last few years and come up with a standard - this loud for a first down, this loud for a touchdown, etc - and broadcast crowd noise in the stadium. When the opposing team has the ball - get a reasonable crowd sound level (no cheating NO and Seattle) to make it a little tougher for opposing QB's to operate. the level could change based on the down and what point in the game you're at (both time left and score) If the league adjusts a standard for all these - it can be implemented across the board.
I think some of this might minimize the creepy feeling of players running into the end zone to the sound of crickets.
Also, think of the opportunity to be able to hear the players yelling out to one another before the snap, etc. A few second tape delay can take care of the inevitable profanity.
