I don't think it's too plain and agree with Cathie that the plain squares will give you a chance to show some of you great hand quilting! Maybe star motifs to keep the theme going?
As for the log cabins - i hope you use them because I really like them but have myself planned elaborate borders then ended up putting a plain one on because my mind and heart are already moving on to the next project! :D
Whatever you decide, it will be beautiful!
K x