Let's start a little higher level than your site design or cart funnel... Those are important but if your traffic isn't convertable or your business isn't appropriate, all the logos and icon tweaks in the world won't fix that.
how are you getting traffic?
how much traffic do you have to base your conclusion about conversion rates on?
are your products your own or can they be found elsewhere?
how do you compare in price?
how do you set yourself apart other than price?
do you have any brand reputation or history people may know?
do you offer unique value for the category like hassle free returns?
do you have a good history of reviews and comments from customers on your products?
why would you buy from your own site?