If you have ever installed a prior version of OS X using your current iTunes account, the full version of the previous version(s) should be available in your Mac App Store PURCHASES tab. You can download it to your Mac and create a bootable USB drive with that full install.
My rMBP shipped with Mountain Lion, and I just verified that I have Lion, Mountain Lion, Mavericks, Yosemite and El Capitan in the PURCHASES tab for download.
Also, the Mac App Store was not introduced until Snow Leopard (10.6.8), so nothing prior to Snow Leopard will be available via the MAS.