All the graphics used in my skins come from images freely offered in public domain backgrounds, wallpapers, or other free graphics directories, for download and use by anyone; or if not, they have been made by myself. I have a collection of thousands of backgrounds and other graphics. The reason I have so many is because I have been collecting them for many years, and because I have been making the graphics for my websites and blogs, for a long time.
There is always the possibility that an image from a free graphics site may have gotten there erroneously, and may be copyrighted. This is a risk that is understood as being inherent in using the free graphics from these sites. They can not always guarantee that something copyrighted did not slip through somehow.
I am very careful to only use graphics offered on free graphics sites stating that they for anyone to use. If anyone sees a graphic I am using, that has been copyrighted, then they must please inform me, and I will immediately remove that graphic, and offer my deepest regret and sincere apologies - it would have happened unknowingly.
Most generally, Fair Use says that graphics may be used for evaluation, educational purposes, or for personal use, and not for profit. Fair Use of graphics could conceivably be violated when the graphic is used to make a profit commercially, or when the use of the graphic detracts from the earnings of the copyright-holder. Neither of which would be the case in using the free graphics for making free browser skins for personal use.
In other words, if someone were to start selling browser skins with copyrighted images, or if someone used another's copyrighted logo to sell something of their own, then there could conceivably be grounds for a problem.
Since these free graphics are being used to make skins which are only intended for personal use and evaluation, and are not for sale in any way, there should be no problem.
As to my own graphics, I don't care what anybody does with them. None of my own are copyrighted and I don't ever expect to profit from any of them. I make them because it's fun, not to make money from them.
My purpose is not to profit from making the browser skins; it is only a creative hobby that I enjoy, and I also like making pretty things for other people to enjoy.
I hope that you will like the skins and enjoy using them!
(Just don't sell them, guys!)

Your friend,
Ava
(MagicStarER)