I’ve had a set of imgur galleries for some time now for all BL3 cosmetics, but mostly they’ve been sort of hidden around in other threads. I figure I may as well post 'em out here as their own Thing, for easier keeping-track-of. Feel free to steal these and do whatever you want with 'em, I lay no claim to screenshots I’ve taken. These tend to get updated within a few days of new content, though of course I make no promises about the future. They’ve been updated as far as DLC4 (Psycho Krieg) content, at time of writing.
Last Update: October 8, 2020 - Added the Porphyrophobia weapon skin (part of Bloody Harvest 2020) that I’d missed in the last patch
ECHO Themes: https://imgur.com/gallery/Uyxfsrx
Room Decorations: https://imgur.com/gallery/ae2GkE3
Weapon Skins: https://imgur.com/gallery/SXbNYy1
Weapon Trinkets: https://imgur.com/gallery/jjjYVt5 (inventory thumbnails only)
Last update: June 30, 2020
The Outrunner, Technical, and Cyclone galleries have each skin on a couple of different vehicle configurations, since those often look fairly different.