I was also going to mention the Mystery Train quilts on QB!
There are many, many, many mystery quilts you can find on line, some older some active. I'm sure you could use most any of them if you get permission from the site/designer. Here are a few I'm following:
[TABLE="width: 831"]
[TR]
[TD]Quilt Art Designs[/TD]
[TD]Wanderlust (PP)[/TD]
[TD]http://quiltartdesigns.blogspot.com/p/bom.html[/TD]
[/TR]
[TR]
[TD]Quilt Art Designs[/TD]
[TD]Calender - Mystery block (PP)[/TD]
[TD]http://quiltartdesigns.blogspot.com/...ry-blocks.html[/TD]
[/TR]
[TR]
[TD]Quilt Addict Anonymous[/TD]
[TD]Stars in the Night[/TD]
[TD]http://www.quiltaddictsanonymous.com[/TD]
[/TR]
[TR]
[TD]Quilt Doodle[/TD]
[TD]Tis' the Season[/TD]
[TD]http://www.quiltdoodledesigns.com/BOM-2016.html[/TD]
[/TR]
[TR]
[TD]Stitchery Dickory Dock[/TD]
[TD]Sugar Block Club[/TD]
[TD]http://www.stitcherydickorydock.com/sugar-block-club/[/TD]
[/TR]
[TR]
[TD]Pat Slone[/TD]
[TD]My Secret Garden[/TD]
[TD]http://www.patsloan.com[/TD]
[/TR]
[TR]
[TD]Claudias Quilts[/TD]
[TD]Houses & Stars[/TD]
[TD]http://www.claudias-quilts.com[/TD]
[/TR]
[/TABLE]
Sorry, I should add a couple of them are only free for a limited time
sorry