The filename for the rendered image of each layer can be customized using the workflow as follows.

To name your render layers

1. From the Render Layer Editor, select the layer that you wish to name.
2. Open the Render Settings window (Window > Rendering Editors > Render Settings).
3. Click on the Common tab. Under the File Output section, right-click the File Name Prefix attribute and select Create Layer Override.
4. Enter the desired filename for the selected render layer.

   After the image is rendered, the image output for the selected layer will be saved under the filename as entered.