When you gather up scraps, you can't keep everything, but you can sure as hell try. Don't underestimate what can or can't be a good addition to the scrap box. But remember, a scrap box is like a closet. Go through it and take out what you know doesn't inspire or intrigue you.
Also have this mindset when you're looking at things like magazines, cutting up scrapbook paper, or leftover supplies that you think is trash.
I know, I know, that's a very hoarder thing to do. But really, it doesn't have to be. Think of it more like rummaging through someone's trash. You know, the whole 'One man's trash is another man's treasure,' deal.
Pick out the treasure and throw out the trash. Then you'll have a full box full of inspiration.