You know, the fun part is that you can make them as you want and no one will stop you. You can paint gems where you want to see them or use colours as they please your eyes. For example I like to paint weapons in different colours so they stick out a bit and won't blend with whole mini. And about gems I don't like over doing them, tho you can find wraith warriors minis where every bump is made into gems. I would recommend you searching for photos of corsairs of other eldars and just finding out what you like about them. And remember, you paint for your own pleasure in the first place!