I've done some NIN fan mixes, generally using only the original source material in hopes of getting an "authentic" sound:
Sanctified Maxisingle: A fan-made hypothetical Halo 3.5. What if Sanctified had been released as a single? Remixes of Sanctified, The Only Time, Terrible Lie, and Head Like a Hole made using only the original source material for a pure/authentic feel (I hope!) In addition to using only original source material, I avoided anachronistic effects (glitching, autotune, etc.). For tracks that have official remixes (HLAH, TL) I have tried to ensure that my own mixes differ enough to justify their existence.
The Slip: Created using only sounds from The Slip and the two bonus Ghost tracks. "999,999", "The Four of Us Are Dying" and "Corona Radiata" are not present as tracks but material from those songs is mixed into the other tracks.
"With Teeth": Remixed using only audio from the 5.1 channels. I've done some other WT remixes that I still need to upload.