Reviews should be Objective in my opinion... facts for what is presented as a product. Being subjective is offering up your own personal opinion, which is what this review is when it comes to theme.
Zach, does the game work out it's theme well, or could the designers have done something better with the theme used?
Remember, Iron Maiden is THE theme... so you are stuck with the theme and should review it as such.
Just my 2 cents.