Paint & crayon Color the entire card with crayons (however you would like), then paint over it with black paint. When the paint dries, you can use a popsicle stick or paper clip to scratch your design.
Mixed Media
Torn & cut paper collage
Fabric with sewing These can be made many ways. A piece of fabric can be glued to the trading card, and then a design sewn on top. Fabric can be cut up and placed on the card
Line Designs with pen/fine point sharpie
Word Art with stamping
Word Art with paper collage
Chalk or colored pastel (drawing)
Paper collage Paper is painted, then cut into shapes, and put on the trading card in interesting ways.