This is not advisable to set UIView background colour (to set an image) like this, instead add an UIImageView as subview of UIView and then assign image it to it. This will be same look like you've setting a background.
However, here's the solution for this,
UIGraphicsBeginImageContext(self.view.frame.size);
[[UIImage imageNamed:@"image.png"] drawInRect:self.view.bounds];
UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
self.view.backgroundColor = [UIColor colorWithPatternImage:image];
Straight from this answer