My wife suggested that we wallpaper a small entranceway to our home. It is a fully-enclosed space (about 3 ft by 3ft) beyond the front door - but there's a second (glass) door to enter the living space. This small room has no vents, and therefore does not receive any heat/air conditioning. It can get very cold in the winter and very warm in the summer. My concern is whether the wallpapering would hold up to these temperatures. Thoughts?
Your entryway gets heat from the house. Not enough for you to call it warm, but it will be warm compared to the exterior, and that is what is important.
Secondly, the room might not be heated, and the windows may leak, but it is also very helpful if the walls are insulated.
The issue is not temperature, it is moisture. Go into the room on a wet winter day and feel the walls. Is any part of the wall wet? Go into the room on a super cold winter day. Are the walls damp or icy? Check near the windows and down low and in the corners where air moves the least and cold is nearest by. If there is dampness, then the wall paper has no chance because the moisture will release the glue even if the paper is vinyl. But, if the walls remain dry, then your wall paper should be fine.