I told you before, I am a HUGE sketch fan, so I use sketches often for inspiration. Here are some sites I like to visit whenever I need a little jumpstart:
Becky Fleck's Pagemaps
My Sketch World
Let's Capture These Sketches
I do have to say, our very own Bree Tetz has a site that I ADORE for card sketches. You should definitely take a look:
There's also a DT call right now at Bree's site, so head on over and create some amazing cards!
I also did a google search for scrapbook sketches, and a TON of images came up. So go ahead and get sketchy, but don't forget, if you are using a sketch that is someone else's, please make sure to give proper credit. :)