There's only one person who didn't offer art, fic, or vids, and I think the voice matches ghostofnuggetspast's podfics. That being said, I can’t find any samples of gardnerhill’s voice, so I can’t discount the possibility that they sound very similar.
Part 2: Vid & Podfic
Dee_Laundry was the only person to offer vids this year and the style of this vid has some similarities to a previous year’s Holmestice vid.
(For those inclined to go sleuthing, I'll save you the trouble: This video was posted to a shared account. Here's an example from a previous Holmestice.)
There's only one person who didn't offer art, fic, or vids, and I think the voice matches ghostofnuggetspast's podfics. That being said, I can’t find any samples of gardnerhill’s voice, so I can’t discount the possibility that they sound very similar.