While designing levels, I've noticed that it's often really quiet when designing, especially when broken up with the sounds and music while testing. I think it would be neat if you could listen to music from LL while designing. It would make the design process a bit less boring and help give designers a feel for how the music will work with the level they're designing, without having to stop and test or pause Youtube videos a lot.
...it would also be nice if you'd add back the music that's missing in the current version of Chapter 2, and maybe patch that into Chapter 2 rather than saving it for later versions?? *cough*