Funny T-Shirt Shop UX Browse Experience

Chummy Tees is an online t-shirt shop that we are looking to improve the user experience with. The site's product page template has recently been updated to better showcase the various styles and options of t-shirts available (e.g. this t-shirt) but are now wanting to focus on the top level browse experience.

We're looking for someone who has past experience with improving conversion rates along with the graphical know how to design something that will look good on desktop and mobile. We are able to modify each "page" as uniquely as needed, but all the t-shirt "collections" urls would need to follow the same format as there are too many to think about individually.