Is it just me or are there really not themes to the seasons/challenges anymore. It seemed like towards the beginning there were and at some point Owl just veered of course and never corrected. I recall there being a thread with theme suggestions that had some good ones that actually had “a theme”, too.
The problem with doing strict themes (i.e. an all Classic Rock week) is if they include EVERY song that fits the theme, it's easy for people with huge libraries to farm LP by playing rarer, less popular songs. So to counter that, challenges have included less songs. The problem with that is, if it's a genre/decade theme, people complain "Why isn't [song] part of the challenge this week?!" If they keep the challenge themes vague, they can limit them to a selection of songs (which they likened to a mix tape before) without people complaining about songs missing (ideally. Some people will just complain anyway).