I have a variety of these 4x6 cards that are single sheets - not folded - leftover from another project. As they are mostly jewel-tones, I'm sort of forced to decorate both sides, since I need them to be "family friendly" for use.
I'm pretty new to cardmaking, but have plenty of papers from scrapbooking. I have a friend who does a lot with stamping and cardmaking and I get ideas from sites like this one. I have a variety of scrapbook papers/products that are more suitable for cards as well.