I worked in games for 3 years and we worked with a few contractors. I noticed a few bizarre things about the contractors we used. We never worked with the same contractor for two different games in a row. Every contractor we used we heard of through word of mouth. They were all small (2-20 people) and most of the time they had no to little online presence. The most effective avenue for getting jobs seemed to be handing your business card out at GDC to as many people as you can.
As far as I can see, if you want to be a game contractor, you're better off starting one on your own than trying to get hired by a contracting company. Find a game artist who's also just starting out, launch a shitty game or two to show that you can, then hand your card out at GDC.