The longer you use Lightroom the more older images you see as you browse through your Catalog. You may not notice them much or bother to critique your post-processing prowess from days gone by but I'll bet there are some images that could use another look.
Let's face it, Lightroom has greatly improved over the years. PV2012 is amazing. So has Photoshop, Photoshop Elements, or whatever external editor you use. If some of these are HDR images you know that Photomatix and HDR Efex have gotten better. Your plugins from Nik, onOne, or Topaz have all updated their algorithms and tools. Heck, you probably have a better computer to run it all by now! Most of all, your skills have been honed and perfected over the years.
Stroll through your catalog. That wonderful post production masterpiece from a few years ago might shock and appall you now. What you thought was a WOW in 2007 might be a lump of lead in 2012. Unlike the Alchemists of old, however, you have the tools and skills to turn that lead into gold. Rework the image. Rethink the image. See what you can make of it today. Remember that Lightroom lets you create virtual copies so you can experiment to your heart's content.
So if you've been a little stuck and can't figure out what to shoot go and look at the past. Your Catalog is a treasure trove of masterpieces waiting to be reborn. That'll get your creative juices flowing and before you know it you'll be back out of that rut!