I love the felt board idea - that one is probably the most age appropriate too. I would cut a bunch of squares, triangles, rectangles, circles... you get the idea ...in a wide variety of fabrics - use fabrics of as many TEXTURES as well as colors and prints - toddlers are very tactile. Terry cloth, denim, satin, tulle, cotton, etc are all good. Let her design away and if you get really adventurous once she really likes what she has layed out let her watch as you peice it together for her