Quake 3 needed some love. There's a handmade HD texture pack, but the textures in Quake 3 all seem to fit with each other to a degree I don't see in some other titles, and the handmade ones weren't very accurate and clashed badly with the originals IMHO. So, upscaling!
Combo of waifu2x and SFTGAN. All world, object and player textures done, though I'd like to tweak some. Textures are of course indistinguishable from the originals at a distance; they just don't get blurry up close. Some needed it a lot more than others. See the skull block on the bottom of the column:
I play a lot of Unreal Tournament. The handmade HD pack for UT99 doesn't stand out as bad: the textures in UT weren't nearly as cohesive. Quake 3 goes heavy on the consistency: it's almost all trenchcoat/fedora skulls and stuff. It can't be done halfway, or with textures that don't match just right stylistically. It also has very detailed textures (for the resolution). In UT99 it doesn't matter as much IMHO. Textures are generally simpler (bricks, metal thing, wood, etc) though they do end up creating more varied levels visually.
Since I'm happy with how UT looks with said pack, but I do play Q3 as well still and didn't want it to have the indignity of blurrier textures, I gave the upscaling thing a shot. The only time it bothers me is in contrast to what is nowadays very simple geometry. TBH as it's usually not obvious beyond the short/middle distance I do wonder if it's worth it, but it makes me feel happy
Some of them scaled better than others (and a few just aren't any better). I'd welcome any changes or additions people have, if they fit in with the originals.
I recommend using this mod together with High Quality Quake (to improve the user interface elements) Moddb.com
and Quake Arcade Assets (better models for the weapons and armor) Moddb.com