PNG ICO ICNS MORE
Network & communications
Pixel
16x16 Free Application Icons
linux, cmd, bird
Black
16x16
PNG MORE
UI
Windows 8 Pack (Metro Style)
linux, Client
DarkSlateGray
26x26
Mixed
IconSweets 2
expression engine, linux, tux
40x40
File, document, Penguin
Social media
32 Pixel Social Media Icons
linux
WhiteSmoke
32x32