I was just fanning through a Bicycle deck and noticed that the faces on two of the jacks are in side profile - the other two are full head on pictures - does anyone know of any reason why this is??

Jax,
I don't know the reason, but it's just not Bicycle decks; all decks have the Jack of Hearts and the Jack of Spades in profile.
(Probably because, without them, one-eyed Jacks being wild would be pointless!)
cheers,
Peter Marucci
showtimecol@aol.com

From their earliest inception the Knave of Hearts and the Knave of Spades have always been in profile, at least in the English pack. No one knows why. One theory is that they were done this way to distinguish them from the other two knaves in the pack.
"Playing Card, History of the Pack and explanations of it's many secrets" by W. Gurney Benham detail how and why the pack that exist today looks the way it does.
An interesting read though some of it's history evidence should be taken with a grain of salt.

Its the suits.. the hearts and the spades are the highest.. so they profile..