This is my submission for "Roaring 20s", day 2 of Dalek week on www.deviantart.com .
Deryn is in a deviation of the pose made famous by Bonnie Parker (of Bonnie and Clyde, the infamous criminal duo). I chose it for her because, quite frankly, Deryn has attitude. You'll notice that she's wearing a dress (loosely modeled from a 20s flapper dress). Realistically, Deryn would not have been able to be in disguise for very much longer than the books, so in my version of their world, she became on of the pioneers of the "flappers", though only her clothing and hair style was true to the flapper reputation. She's always loyal to Alek, as he is to her.
Alek is wearing a nice sweater (from an advertisement I found online from the mid 20s). He's being all cute and staring lovingly at Deryn while she's being all B.A. and stuff.
Their car is a 1925 Chevy.
I free-handed all of this, using photos as references for Deryn's pose, Alek's sweater, and the car. The hills in the background were admittedly random, but I thought a city-scape would be too large of an undertaking for my yet-amateur skills.
Thanks for reading my blether :)