Icons are organized according to shape, subject and other icons. Each of these are in turn organized in clear categories. Spanish as you can see, which is very well organized into distinct categories. The quality of selection is good. You get the idea.
Quality is acceptable.
Amazing because of the organization as well as quality of graphics. Because these buttons are all designed similarly your site will have a cohesive feel to it. One could search the net for ages and never come across a site like this one. Debbie's Web Graphics - This site is one page in size but it contains links to lots of others sites containing tons of GIFs. I don't know.