I know it sounds a bit like angels on the head of a pin but I bring this up as I stumbled on this little picture of a Dobby-like Harry Potter gnome and am also thinking about a movement from Pictures at an Exhibition called Gnomes.
If I look at the picture I can fairly and easily make out a story to tell a grandchild who really needs to know that gnomes are here and there in the world and we should look for them (not under bridges as those are trolls - keep things straight please!) and not be afraid to find them.
We can also listen to music and see them in our mind's eye...particularly if you look hard enough and listen with your eyes wide shut.
Imgination is so powerful. How do you teach it or is it just there - or not.