Just a friendly warning from getting yourself and others who may use your artwork into legal copyright trouble. Clkr is strictly for Public Domain contributions which means you cannot upload already copyrighted work or derivatives from such works. You have no legal right to use these. You should read about "Artwork copyrights and licensing" before uploading work to Public Domain. Don't use anyone else's artwork, even if you alter it and do not use it in your projects unless it is allowed by the original creators and only within the specified limits set in licensing. It is a very complicated and dangerous area. I hope this helps you start understanding the issue and keep out of trouble.