on my laptop they are to big full size, but desktop the are good.
personally i think that people like to see the whole "picture" when they are rubbing one off, so as long as it is big enough to fill the screen, all the better.
only way to find out is to run some tests. I know when I did this a while ago, the bigger images did better when compared to conversions, but im also pushing some niches that people may like to zoom up on
