I am new to the challenges--can we enter more than once in a challenge? I couldn't decide between two cards, but I'll make a choice if I have to!
Collage stamps work great for this puzzle style of paper piecing. Using the same color family creates a subtle look. For more pizazz, go for bolder colors that are opposite on the color wheel.
Best of all, for every color you use, you can get that many cards!