Bro DR
I know that the Prophet SAW disliked anything that would distract from prayer, as goes the incident about the designed prayer cloth he SAW had. However I think the direct implication is for the musalla area, the place where prayers will be performed.
One could though question the very foundation for being aesthetic in Islam. We like to see things that please our eyes and satisfies our desires be it in the form of interior decoration, makeup, flashy dresses or anything. So what benefit do we gain from decorating a masjid versus having it plain and simple. Are we justified in decorating parts of the masjid which are not intended for prayer?