All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.
The prayer in the mosque which you mentioned in the question is valid, and putting an image of the door of the Ka’bah and decorating the mosque in general are among the disliked things as we clarified in Fatwa 90090.
We advise the brothers who are running the mosque to take off that image from the direction of the Qiblah of the Imaam so that it would not distract the congregation during the prayer.
For more benefit, please refer to Fatwa 91639.
Allaah Knows best.