I like the idea, it has a lot of potential, but I don't think that this works as a puzzle if runes are generated automatically (unless there's some really clever algorithm underneath to make sure a solution exists).
I've spent some time fiddling around with those runes but I'm pretty sure some of those combinations are impossible to solve ;)
As for the visuals - they're nice, but it's a combination of different (even very different) art styles and even techniques (vector characters and photos). I think it's best to stick to just one, there are lots of free assets pack out there.
I don't want to sound overly negative, I really liked the core idea!