I can help you a bit with the terrain maps and the masks. c: Also, I'll tell you how to put music in.
In the map maker (tools, map maker) in the second tab there should be a form that says music. Put the music file you want to use in C:FeralHeart(or FHPLUS)/Media/Music and then put in the file.(Ambient.mp3, etc.) It should work.
Be sure to save it. You do the same thing with the terrain and masks once you have them made. Save them as PNG's and put them in your Media/terrain files and make sure they're named like mapnameTerrain.png and mapnameMask.png or else there's a chance it won't work. If you're having trouble /making/ the terrains and masks, I have a secret that'll help you. :3 If you have a msn, tell me, because it'll help me with explaining to you how to make them.