The problems will come if the corners of the room and the ceiling joins are not exactly square. Anyone who has done any wallpapering at home will know what I mean. As the paper turns the corner, any anomalies will change the angle of things and could make the illustrations for the adjacent wall travel up over the ceiling! When you are wallpapering round the corner with a normal, patterned wallpaper, you stop at the corner to create an overlap, levelling things up anew, to make the paper continue straight. But overlaps and changes of angle could mean tigers with lumps missing, headless librarians and all sorts - Aaaargggggggh!
It is an old building, so you can see why, as well as being excited, I am a little anxious, and why I am very, very, very glad that a professional is doing the installation, not me!