When you think of a shower base you probably visualize those fiberglass ones that you can buy at big box stores. They work, but they also look pretty generic. If you want to have a custom and classy look in your bathroom you are going to have to pay an expert to pour...
The usual way to tile a custom shower base is to install a liner and adjustable drain, and then pour a concrete shower base. After the concrete drys you tile the floor. This process is slow and time consuming, but yields a good result when you use an experienced tile...