Currently the 4E ruleset makes the green / yellow / red underlays progressively darker the more wounded a token is.
So one solution would be to make the underlays much darker for incapacitated tokens. Not sure if a similar underlay effect (or even the same effect) would help for Shaken tokens too ? For Wild Cards, could progressively darken the underlying for 1, 2 and 3 wounds too.
Another thing that would be good is to add the status onto the token tool tip, so players / GM can hover over foes to see their status.
Any other visual things we might try to increase visibility of statuses ? Can thought of colouring the selection halo, or adding a halo, but this might get confused with targeting, esp. with multiple players targeting things with differing coloured target halos.