Desktop rice before the days of i3-gaps and neon color schemes. Blackbox and its forks were my favorites, and there were even ports to Windows that let me join in on the fun without jumping to Linux. Windows rice in general was at its peak too with all kinds of shell replacements and widgets.
Also old con photos. I remember being in my teens, seeing all those fun meetups like the ones 4chan used to do at Otakon, and thinking to myself "man I can't wait until I'm on my own and have money so I can do stuff like this". But by the time I got a decent job and moved out, they apparently became highly corporate, political, and overall uncomfy. Plus I'd probably be a fish out of water since I don't care for modern games or anime, just stuff from the 00s and before.