Is there a Lomography picture style software for Canon 50D, are there custom camera settings I could use to achieve a similar effect?
No built in picture style exists for lomo on the Canon 50D camera.
Basically you just need to add a vignette, and do a cross processing style that you can achieve in most photo editing software. You also may want to add fake light leaks to get the full effect.
A tutorial for the effect can be found at digital photography school here.