While I personally would love an Iron Maiden theme, I doubt it will ever happen. The Bands that they have used have significantly more sales than Maiden (AC/DC 200M, Stones 200M, GNR 100M and it was released at their peak). Metallica may be the best comparison with 110M sales.
However, if they are going for sales and popularity, Aerosmith is the obvious choice for a band theme. They have 150M in album sales.
Iron Maiden is closer to 90M but they are well past their peak and it would appeal to a core audience.
I guess you could argue that they are only trying to sell 3000 pinball machines so you only need to appeal to a core fanbase.