• Are there specific textures for the ClassiCube? By "specific" I mean textures made for the game, not those adapted from Minecraft and other games.
• If these textures exist, where can I download them?

Not really (from what I know of) they are just textures, you can also download texture that other people have made.

I created an original texture pack for ClassiCube, which is currently used for the steam and webclient release.
You can download it here: https://static.classicube.net/default.zip

14 hours ago, COERSA said:

not those adapted from Minecraft and other games

idk what you mean by this but there are a bunch of texture packs that work with the default blocks here : https://123dmwm.com/texturepacks.html
any other global or level blocks that a server may have will show up as purple error blocks