I remember when the wave serpent was designed as a boat with a huge shield surrounding his weapons... I´m talking about times when the epic 40000 game was called "Space Marine".
Don´t know why, but I really liked this design, I suppose I liked it for its alien look, but I have to say the actual model is pretty good and fits more the eldar look of today.
The wave serpent is the only decent way the eldar have to transport their troops around the battlefield (no, the warpgates aren´t in the rules and I consider the falcon more as a gunship than a transport) and with the shield and its speed is a decently safe one
The serpent is a fast and gravitic transport so you can zip your troops from one corner of the table to his opposite in a pair of turns, or more turns while firing a heavy weapon, which is a think to consider.
The main role for the wave serpents in my army is to carry a squad of dire avengers and the squad of howling banshees thile providing anti-tank support (with twin linked bright lances).
My wave serpents are totally painted in blue, with a stripe along the main section of the hull that ends in a straight line in the left wing.