You didn't mention an important feature of the Russian accent -- the peculiar rhythm. Russians tend to pronounce every word separately whereas you native speakers join words into clusters. A good example of it you can find at the beginning of this video:
http://www.youtube.com/watch?v=86oL5Wje ... re=related

What is "wrong" with this example is the r's, which are too good. For a really heavy accent you should do proper Russian r's, if you can.
Perhaps even more important is to do proper Russian h's (who, history, ahead, perhaps etc).

Of course, these are only the tip of the iceberg.