There's not much room for more than 3 productive WR's, and those will likely be Jackson, Curtis, & Brown when all are healthy.
Baskett is a bigger target at 6'2", which is a different look from the 3 guys above, and he's got a knack for scoring on long plays - 4 career TD's: 90,89,87, & 10 yard catches. In theory, the fade should work well as well.
Avvant is another more physical guy, who technically is 2nd string, ahead of Baskett. he had a good game as well, just not quite as flashy. I think he was other WR down the field on the Baskett catch - McNabb likely had a TD to either of them.
Lewis is really just a depth WR, and is behind Jackson on the depth chart.