SilhouettesSilhouette art already exists on some wall decor in the game if you have Supernatural, but this is a nifty trick to being able to create your own.
You'll have to decide what to use as your silhouette beforehand, it can be anything from an object, to a pet, to single sim doing a crazy club dance, a mother tossing a toddler into the air or a sim couple kissing.
For my main example I'll be snapping a sim couple slow-dancing.
http://imageshack.us/a/img11/6528/screenshot51m.jpg "width=640" "height=480"
I have prepared my wallpaper backdrop and chose sims - the only things that matter on your sims (if you're using sims) is anything on them that makes a silhouette: their facial features, the shape of their clothing, the hair. Colours do not matter at all, but be sure to choose the kind of clothing that has all channels recolourable, or atleast the ones that aren't recolourable be black or a dark colour.
You want to get rid of any lighting in the room and only have a few invisible lights illuminating the wallpaper. Fetch the invisible lights from BuyDebug menu. ("TestingCheatsEnabled on"->"BuyDebug", Misc. section) I'm using the horizontal lights as opposed to the ceiling ones.
Now, chances are even with no light directed at your sims, they are still relatively lit-up with all of their features visible. This is where we "turn" our sims into silhouettes. Power up the "TestingCheatsEnabled on" cheat if you haven't already and shift+click on your sim(s) and choose "Edit in CAS". Make their skin black (grey colour slider to the max) and also make their clothing black all over and if their hair is a light colour make it black as well. If your female sim had bright or light-coloured makeup on, remove that or make it black.
I've decided to spice things up a little for my photo and left certain elements red - the rose in the lady's hair, her dress and the flames on the male's clothing.
http://imageshack.us/a/img217/5593/screenshot52y.jpg "width=640" "height=480"
Don't worry if you see tiny things that are still not black - buttons on clothing, slight light reflection on the skin, the whites of the eyes. Photographs are always a little bit darker once they're taken, so those elements should be dark enough on the actual photograph.
http://imageshack.us/a/img688/4476/dancersh.png
Don't feel like snapping sims dancing? How about good old Victorian profiles?
http://imageshack.us/a/img18/4138/sil1v.png

http://imageshack.us/a/img443/4731/palm1v.png'>

http://imageshack.us/a/img6/5861/palm3.png
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http://imageshack.us/a/img546/766/screenshot56t.jpg "width=640" "height=480"
http://imageshack.us/a/img607/2157/screenshot57x.jpg "width=640" "height=480"