The graphics in L4D2 are somewhat disappointing, at least in some regards. First off, the title looks all too similar to the original L4D, which was an underwhelming title in terms of its visual quality. Secondly, the environments look flat and grainy while the character models are simply unappealing. Lastly, the returning special infected (zombies) show a major lack of progress as you can't, in any way, spot a difference between their appearance in this title and the original.
Happily, I can report that there are some positive points to make a note of. The level designs themselves (regardless of the quality in which they were implemented) are very diverse in regards to concepts and color palettes used, so that is a major plus. Also, the combat effects are spot on, such as the sound and look of slashing a zombie with a katana being nearly immaculate. The gore and destruction is shown well with different parts of zombies being torn off, slashed apart, or blown off with accuracy in terms of place of impact and the visual effects of the injury.
In regards to music, there isn't really much of it. You have some piano cues which signal the presence of special infected along with a few cryptic scores to accompany certain firefights. It works, but doesn't go much beyond the score of satisfactory.