Etsy.com, Shutterfly.com and VistaPrint.com are good online resources for designing unique, custom cell phone covers. Some larger retailers, such as Walmart and Target, sell custom covers through their photo departments.
Depending on the style you are looking for, you can purchase custom cell phone covers through several retailers. Shutterfly.com, VistaPrint.com, Target and Walmart are good options for designing a cover with personal photos. You can also add your own text, depending on your design choice. Etsy.com offers photo options as well, but has more design options since there are a large number of designers who sell personalized phone covers through the site.