I can FastBoot my device. How can I reinstall an Android image to it?
If you can find a ROM on a forum or website, you can easily flash it using fastboot - as long as it supports fastboot flashing.

Most ROM makers provide both types of ROM flashing mode.

To flash, you should have a .img file (most likely called system.img). You can flash this  by connecting your device in fastboot mode to your pc and using this command:

fastboot flash system C:\path\to\system.img

This will then flash the image to your phone. Once that is done, erase your user data using the fastboot -w command.

You should then be able to use your phone with the new ROM, and it should boot correctly.