When image pixel is configured there is no requirement of &click_id= parameters in pixel as like in the case of global postback.
Example : <img src=”https://tracking_domain.com/c_tr” width=’1′ height=’1’/>
Image Pixel can be used with other parameter like : Goal, Sale amount & Order ID etc
Goal : &goal=
Sale amount : &sale_amount=
Order ID : &order_id=