Don't get me startled on this but I am not a fan of Redesign Concept because a lot of time (Not trying to be general), designers tend to forget many aspects of what's behind a redesign like:
A lot of artist and designers around the globe love to make redesign concepts for the most used apps and websites, and most of these jobs are very well done and deserve more attention. Because of that was released a website called Redsgn.Co, a collection of redesigns, concepts or real.
But Redsgn.Co it's not only about concepts, you can find real redesigns and their case studies, most of them redirects for a external page, a blog post from the designer who makes the project. It's a great library to make some research or find inspiration for your next project.
Curation of functional and aesthetic redesign stories. These stories will walk you through the steps and results undertaken in making better products.
Take a look on some of the cases are featured there: