Bootstrap developer to update UI/UX of current site

Our site is nearing Beta testing stage. It allows users to create their own T-shirt (and other garments) shop, selling stock designs and adding their own designs. The developers have done a fantastic job of making everything work, but we are aware that the look is outdated and needs modernising. The site is created in Laravel/Bootstrap so we seek someone with experience of this platform with UI and UX knowledge that can work with our own designers and current developers to create a modern, simple to use and impressive to see web experience on desktop and mobile.
Additional challenge is that our users, once they create their own shop, are able to personalise their space so that their shop is unique.