I made one bargello quilt. I bought this book
http://www.amazon.ca/gp/product/1564...ls_o01_s00_i01 which explains not only a construction method, but also how to draft your own design. I don't think the construction method would be great for a bed quilt (mine is a wallhanging) but it might give you some ideas how to proceed. Here's my quilt - designed to look like a waterfall.
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