Slackware is known to be a Linux distribution with minimum patches from upstream source code. Meaning that you won't see fancy cosmetics accessories when you installed Slackware. Everything is build using the upstream code (aka vanilla source code). Sometimes, patches are done in the code, not in the UI, so basically all the UI are still genuine from the upstream.
But that doesn't prevent Slackware users to improvise their machine to be pure plain. You can change that. Wants some proof? Check this movie on YouTube. It's based on Slackware 12.0, but i guess it can be used for Slackware 12.1 as well.