Covering up venue eyesores - need ideas please!

For the bright picture, you maybe could have a free-standing narrow sign or banner on a pole. to block the bottom of the red conduit. Another option is to hang material from the conduit -- like a valance. Also, you could maybe have a cardboard column -- sort of a v-shaped piece to the height of the door -- like cutting out the corner of a cardboard box. Cover it with nice material. Put it at both sides of the door just before the bride enters, so the pictures can look nicer. But you have to have those removed quickly from the fire-alarm side since code enforcers would not approve of that.

For the darker room, you could set up a backdrop of plastic pipe with maybe white sheeting overlaid with sheer material, and angle it 30 degrees or 45 from the stairs. So the cameraman would be taking a picture directly toward it. Secure part of it the stairway.

Photos can be edited to block off the anything beyond the backdrop.

These options are assuming you do not hire another group to decorate.