1. Download this mod : https://www.nexusmods.com/mysummercar/mods/5692
2. After you downloaded the mod put the texture you like in “My summer car\mods\assets\carpet“
3. Rename the texture to “carpet_texture“

If you want to have more textures in the carpet folder rename the texture you dont want to use
at the moment to “carpet_texture1“ (you can have as much as you want of them 
just change the number of the next one for example to “carpet_texture2“) 
and the one u want to use to “carpet_texture“

Creator of the mod : https://next.nexusmods.com/profile/tuzyara?gameId=2600