I'm not sure if it's a great idea performance-wise and storage-wise (more thumbnail creation) but sharing it for discussion here, plus it is simply to implement.

Only your personal authored files because, again, performance - it's more likely that you're looking for a file you uploaded yourself a while ago but all your filenames start with Screenshot From 202... because who really thinks about file names these days when uploading to Phorge.

https://phabricator.wikimedia.org/T135729#10665881 includes a quick implementation as Phorge already offers a PHUIObjectItemView::setSideColumn() concept (with strange hardcoded widths though).

Screenshots per the three CSS widths that Phorge differentiates on: