I now have come to appreciate the value of leftovers in flower arranging as well. I like to save the bits and pieces that are unused at the end of an arranging project with silks. Sometimes it appears that there isn't anything worth saving...a little flower here, some leaves there. But you might be surprised what you can do with some little things--and a few big things as well.
I have a room with a few shelves of vases of different shapes and sizes. The little painted pot above was one of the items in my collection...who know from what, when or why...but it's been sitting there quietly for several years. After deciding to make a miniature arrangement for a friend's birthday, I chose this cute but lonely little pot and noted the colors painted on it. I then explored my "extras" bins, which are all organized by color--a bin for the pinks, a bin for the blues, a bin for the yellows. You get the idea. I found a few little pieces here and there that matched the pot's colors, and within a few minutes, I had a little flower arrangement that consisted of things that were too small for a big project but just right for a 4" pot.
Here's another leftovers project. I had used this container for some fresh flowers and was in the process of putting it away when I decided it would be nice to have a red arrangement in my living room for the month of February. So I went to my red bin, checked out my options, and voila--a red arrangement. A few stems of this, three of that, some random grass and leftover sticks. Some of the items had been previously cut, so I inserted them into spots that worked well with their pre-determined height.
You just never know how useful those "scraps" are going to be someday, so quit complaining and be grateful!