I also used woody prunings as a mini log pile. I put them under shruby plants to create a mini-habitat. You could put them under hedges too (I don't have any!) They will rot down eventually, giving insects, amphibians, etc, a home in the meantime. And it's much more environmentally friendly than taking them to the dump.
I also have rock piles (well - mostly slabs and bits of concrete), in shady areas. And I leave a few terracotta pots on their sides to give things a place to hide.
Oh and for amphibians, you could bury a few terracotta pots (with the opening in the side of a hill, if you see what I mean) or terracotta drainpipes to give them a place to hide and hybernate. (mine live under the decking by my pond. It's so cute - they've sealed most of the entrance with mud and dug themselve a small gap to get in and out!)