I would like to take a room in my house, and attach trellises to the entire surface of the 4 walls, held about 1 inch off the surface of the wall. I would then like to train ivy up the trellises. I want it to be thick enough that the trellises and walls are entirely obscured.

I would very much like to hear from someone who has done this, for a more in depth conversation.

I'm open to any changes in tactics or plants, as long as my vision of 4 solid walls of green is preserved.

Things to consider:

Light: Even ivy needs light and unless your room has a glass roof there is unlikely to be enough light for plants on every wall.

Growing medium and containers. To have ivy over every wall you would need pots or troughs all around the room.

Access: If you have trellis 1 inch away from every wall how will you access power sockets, light switches, etc? How will you clean/redecorate the walls?

Dirt: Indoor plants do not get rained on so somehow you will have to get the dust off your plants without damaging the wall beneath. Free standing or hanging plants can be rinsed off in the shower but yours will be permanently stuck to the walls.

Aerial roots: Ivy is a self clinging vine. It will not stay on the trellis but will try to stick to the wall.

Time: to achieve this effect would take several years providing all else went well.

I have seen this done on internal courtyards (no roof.) But only with undecorated walls to which the ivy sticks by itself and in a milieu where hosing it down periodically to clean the leaves does no harm.

If you go on over to the Houseplant Forum you can ask some of the regulars to post pictures of their rooms. Some of them live in mini jungles. But the plants are not fixed to the walls.