Besides playing official Doom IWADs, you can also make your own. There are many programs made to do this. With these programs, you can make a Doom WAD of your very own
Programs for making a Doom WADEdit
There are many WAD maker programs that you can use to make a Doom WAD including Doom Builder, Doom Builder 2, and SLADE. Doom Builder and Doom Builder 2 are very good tools for making levels and Slade is a good tool for editing the artwork in WAD files.
Using a WAD maker ProgramEdit
First, you have to configure your Doom resources so that you have something to work with. You can get the resources from any Doom WAD file. If you do not own a copy of Doom than you can use the Freedoom WAD for your resources. Then, you're ready to make your Doom WAD.