Not bad at all! Jokers face and hands look find. Batman needs some more details (mainly on his chest area). Background could also be more detailed - I mean you really should draw a real background not just red and yellow mess.
I've got problem with the angle of batman's head. I mean that costume doesn't really allows him to bend his neck AT ALL. So if the torso is vertical - and it is - than the head should be vertical too!
Joker's hip also looks odd - to be honest he doesn't really look like he has one.
Promising picture, keep it up!