Probably the most often cited source for inspiration is creation/nature. So if you're stuck in Designer's Block, perhaps look to creation for the some inspiration? There are many ways to look for inspiration in creation and the following are probably just the tip of the ice:
-how it makes you feel
When evaluating a potential source of inspiration always keep in mind your personal style.
Beauty, is probably the most often way in which creation inspires design. Just look at all the Art Nouveau artwork?
Do you do a lot of work that has an "edge" to it? Then instead of finding inspiration in creation's beauty, perhaps consider finding inspiration in its danger or things that, instead of giving you a warm fuzzy feeling and wanting to say "awwww," are typically seen as being creepy, phobic, and make people's skin crawl? Do you have a fascination with storms, volcanoes,.... these could also work for inspiration. Do those things frighten you? If so, they can still be a source of inspiration.
-How it makes you feel:
You can also design from an emotional response to creation. How does that storm make you feel? Small? Frightened? Elated? Why not try and design a piece that represents that?
Perhaps storms bring back memories, or you've lost a loved one because of a natural disaster? Why not use that as an inspiration to make a piece in remembrance of them? Or commemorating that childhood memory?