I designed these because I wanted some custom icons for my smartphone. I made them as PNGs, but decided that I owed the site some work as I haven't contributed in a while, so I converted them to icons too.
These aren't perfect - I made them very quickly, and just ran the icons through the image to icon converter. Thus, the set is not optimized to show the smaller icons well. There are quality issues too, but oh well.
Feel free to alter any of them for your own use, but I do ask that you not re-upload them or any altered versions of them.