iOS Custom UITableViewCell and backgroundImage

[arnieterm]

Hi all
I have created a custom UITableViewCell for a grouped tableview. As we know in grouped tableview the cell appears with round corners. I have to set background image of each cell also using the below given code

UIImageView* vwimg = [ [ UIImageView alloc] initWithFrame: cellFrame];
UIImage* img = [ UIImage imageNamed: @"round.png"];
vwimg.image = img;
cell.backgroundView = vwimg;

All this is being done in cellForRowAtIndexPath method. My problem is that the images do not occur as round.Do I need to use round images or does there exists any alternative for this?
Also do I need to set every element on this image with a "clear" color?
Thanks
Arnieterm