I haven't played Masque of the Red Death, though I bought it and read it.
I ran a GURPS game with a
very similar premise,
set in London in 1888.
I love the period and it's very suitable for secret magic, mystery and monster hunting. Offers both cool technology and extremely plausible ways to make the PCs rely on primitive methods, because much of the world is still stuck using them.
I very much recommend the British TV series
'Ripper Street' for period feel and inspiration. Not quite as good (though still fairly entertaining), and more apropos for monster hunting in Victorian times, is the series
'Penny Dreadful'.
The fairly recent film
'The Limehouse Golem' was quite good.
For play in the US, I have high hopes for the new series
'The Alienist'.
It's superfluous to mention Sherlock Holmes as inspiration for Victorian gaming, so I won't, but let me just mention one particular non-canon movie that I recommend, for reasons that should be obvious,
'Murder by Decree'. Much better than
'From Hell', though that is, I suppose, a decent source of gaming inspiration as well. And while it has nothing in particular to do with monsters or traditional horror gaming, allow me to mention the movie
'The Seven-Per-Cent-Solution' (as well as the original story) as another non-canon Holmes adventure that I enjoyed immensely.