-A picture of little kids. Color their shirts (like a light pink or blue) or any objects they are holding.
-Not sure if this qualifies, but take a picture of a crowd and choose one of the people that stand out and keep them in color.
-Take a cat picture and use spot color on the eyes; green or blue work nicely.
-Clear off a desk and set a coke bottle on it; color in the red parts of the bottle. Put some books/textbooks on the desk, but keep those in black and white.
-Find a picture of a ballerina that is wearing pink; keep the pink color/enhance it but keep everything else black and white.
-Take a screen shot from a video game and use spot color there. Katamari Damacy is a colorful game.
-Find a picture of a laptop with a colored casing.. Dell's Inspiron line would work well.
-Know someone with wacky colored hair? Use them!
Hope at least one or two of those ideas work for you. :)