Oh! Oh! Get accurate album art for ALL of your music!
That was my project a few months back. Took two weeks before I finally finished tracking everything down.
I already get album art for EVERYTHING! If the soundtrack came from a DVD I use the DVD cover. The only problem I have is my OCDness with album covers, they must be divisible by 5 on each dimension. 702 x 584 pixels would be unacceptable. I'd try to shrink it down to get everything nice and even. If I couldn't find a some nice even dimensions at a reasonable size I'd crop it.
I also have all my music ReplayGained. I should fix my genre tags though. I only use 1 genre tag per album.
Oh and I don't use the album artist or composer tags or things like that, just the artist tag, which makes things a bit tricky sometimes. But if I decide to start using them then I'd need to go redo my entire collection. Maybe one of these days though I image it would take years.