I have limited space, a single Billy book case and a square glass tower from Aldli.
I tend to put a line on a shelf or two. I nearly always face off autobots against decepticons across the shelf.
I have maintained a movie shelf for quite a few years now, sometimes it's two shelves.
Newer lines gradually push older lines into storage. I sometimes (rarely these days) display a G1 character next to the modern version.
I have a couple MP shelves, a couple 'generations/comic characters' shelves and a RID shelf (which is over full)
The tower display tends to contain exclusives and more 'collectable' figures, mostly club/Botcon toys.
for pics see my fan interview with Big Trev, (Link below)