This is a table which probably won't help anyone but my daughter, who needed a table on the top bunk bed. Rather that drill in to walls, this was the idea. It fits perfectly and is surprisingly strong.
Designed to slide on to 2 rails and not be obtrusive or dangerous, it's simple and works really well. Maybe it will inspire others to do similar. Designed in Blender. Printed on PLA on Creality CR10S Pro V2 at 0.2mm LOTS of supports (too many, would redesign if I did it again) printed on it's side (as a triangle shape looking down) Dimensions: W-25cm D-17cm H-17.5cm

EDIT - nearly 4 years later 20240909: Thanks to those that are inspired or used this item. I never thought it would really be of use to anyone, but considering it may well prove to be useful to somebody, I'm uploading the blender model for anyone to have a crack at adjusting for their own use.
Have at it and enjoy! BTW, my table outlived the bed it hung on! :D