Oops! I was thinking guild activity. You said "challenge". Our guild does a theme challenge every year. Everyone who wants to participate pays a small fee for 3 fabrics (everyone gets the same fabrics) And it is a challenge to incorporate the 3 fabrics into the same quilt! The quilt must be at least 20 x 20. One year the challenge was that the quilt must have a house in it. Another year the theme was "Under the Sea". The entries were truly amazing! No one is to know which quilt belongs to whom; they are returned in a brown bag, then displayed and judged by the guild members. The winner gets a ribbon and $25, then there is a first and second places. Fun!