1st off WC, i do not understand why i was singled out for funny looks in your questionnaire.. it sounded funny, or humorous, but made no real sense to me.
secondly, entity lighting doesn't look bad at all, its the application that is usually at fault, i almost always have to work at getting my lighting correct, and i am sure everyone else does too, but the fact remains, the successful mappers who get the lights perfect, didn't just happen to do so, a LOT of trial and error goes into it. usually , as in my case, its an intricate combination of ent lights with texture ones mixed.
3rdly.. my contest map double_trouble had music, you may or may not recall this, but the fact is, it did, and the song chosen actually enhanced the play IMO 100%, it set a real mood to the atmosphere, so it can be done.. i suggest only songs with no words, and songs with a long enuff repetition to allow looping, but not so short as to have a noticeable end/beginning if
"IF" you do edit the song.. my song is played out in its entirety, so i didn't have any noticeable chopped out place, it began, played and ended, then began again.. most people chop it in half or so, then end up with a noticeable skip spot.
lastly, HL will give warning messages about improper sized formats or some-such, but the fact is, you can make songs pretty thin, in the sense that a 1 megs file at blah blah settings is how HL wants it, but you can reduce the settings by half and end up with a 1/2 megs song that plays just fine, with the complimentary loading error messages, but the song... plays just fine.
my suggestions are, experiment on the lights, get it right, or it will tell on you in the end as someone who can't get the lights right..
as for the song, test it in a small map, small maps always load with a minimum or hassle, and will allow you to concentrate on the song.