I agree with Sarah. Maybe I'm missing something, but to the question "does something have to be a solution to be interesting/or is something interesting always a solution to something?" I say absolutely not. "Interesting" I think deserves the same treatment as purpose, as imposed on/interpreted by an observer/something second-order. Being external, I don't think that implies that the interesting thing is solving a solution or that there is an inherent purpose within the thing that is to try to find a solution/meet a challenge. Though, I don't mean to say that nothing that is a solution isn't interesting, or interesting things aren't solutions, I think that's actually the case more often than not but it need not always be so.