I use them as a reference when doing butterfly artwork. I thought one day it might look interesting to create a simple black and white fabric pattern using the butterfly outlines. I just needed to do a few things like create digital and neater complete versions of some of the outlines, import them into Photoshop, clean it up, arrange it and slice and dice that to make it into a seamless repeat pattern. That's all... I let that stew in my brain awhile and played with different art apps on my iPad until I found one that had a line I liked and the controls I needed to make the reflected drawing. Once I solved that problem I made a few butterfly outlines.
The next step is to import them into Photoshop (I use PSE8), extract the line objects so I can move them around and change their size or clean up edges. Fairly simple things easily done in PSE. Somewhere along the line though I decided that instead of doing black on white I would do white outlines on a dark background. I choose a dark indigo blue as the background color. So the next step was to make my butterfly objects white.
Add some more butterflies and throw in a little crosshatching texture with a Photoshop brush tool.
Add some little flowers.
Now I'm getting somewhere.
Now do it all again in a perfect square. Try to make a balanced arrangement, slice it, rearrange the pieces, fill the center, finish the crosshatching and tadah...
an indigo butterfly seamless repeat pattern.
And I will probably do this all again, make more flowers, add vines and dots, draw new butterflies. This was a first draft exercise. I want to refine it and eventually have it printed on fabric to see how it looks for real.
You can find instructions on the web for creating a seamless repeat pattern.