Yesterday I looked at two colour 12" blocks on quilters cache and found these easy to piece blocks: Baby Bunting, Blazing Arrows, Broken Dishes, Broken Sugar Bowl, Envelope Motif, Hourglass #4, Jacobs Ladder, Pieced Star, Ruins of Jericho, Solitaire, Solomons Star, Star Puzzle, State of Arizona.
You might also want to check out the Missouri Puzzle block on the same sight. It is a 14" or 15" block.
Good luck.
Will look forward to seeing what you chose.