Praying individually in a Shia masjid

Answer

It is permissible and valid to perform salah individually in such a masjid, provided it is clean and no clear disbelief or acts of shirk are present. However, it may be disliked (makruh) due to the presence of the symbolic element mentioned, which is contrary to our belief — it is better to avoid praying there if possible. *وَتُكْرَهُ الصَّلَاةُ فِي مَوْضِعٍ فِيهِ مَا يُشْغِلُ الْقَلْبَ أَوْ فِيهِ صُوَرٌ أَوْ شِعَارُ أَهْلِ الْبَاطِلِ* — "Prayer is disliked in a place where there is something that distracts the heart, or where there are images, or symbols of falsehood." (al-Bahr al-Raʾiq, Ibn Nujaym)