There was just something in a quilting magazine (McCalls quilting Sept/Oct issue) about having a successful raffle. One of the things was to make sure the quilt was queen size and that it incorporated 8-9 different fabrics. If you only do 2-4 colors it gives people a reason to not buy a ticket "Those colors don't match anything in my house". Another thing they mentioned was having a little info sheet with the raffle about how much time went into making the quilt, how much it cost etc.
I know you asked specifically about a pattern and I'm not answering that for you... sorry :( I don't have a pattern idea, but I thought the 8-9 fabrics was important to mention. The article specifically mentioned that if it was a church raffle that "a traditional quilt is a must. Classic pieced designs are universally loved and, while not absolutely necessary, a little applique goes a long way."
Hope that info is helfpul to you :)