i want to place an image or a content coz the site is pretty wide and the leaderboard is not covering the width of it, so the design is looking very odd with lots of whitespace around adsense...... so i was thinking of pushing the leaderboard to one side and putting image on the left
I've seen plenty of sites with the company logo at the top-left of the page with an AdSense leaderboard top-center or top-right. I see you have another post about trying to increase CTR on your ads. I'd make sure that the image does not draw attention to the ad block though.
It's a common design solution to have an image(height:90px) on one of leaderboards's sides. It makes the page look "whole" and doesn't scare users. As long as the image is at least 20px far from the ad and the image doesn't encourage users to click on the ad, google is fine with it. It's up to you.