PNG ICO ICNS MORE
Gloss: Basic
wrong, warning, Alert
SteelBlue
32x32
Oxygen
notification, about, Desktop
128x128
Gnome 2.18 Icon Theme
LED
warning, Error, wrong
16x16
Simplicio
Alert, warning, Application
Primo
Blue, wrong, Alert
Silk
exclamation, Alert, layout
Error, wrong, Alert
Error, warning, Alert
warning, wrong, Alert
Silk Companion 1
Disk, exclamation, wrong
warning, exclamation, Alert
Fugue
water, exclamation, wrong
globe, earth, Error
charge, Battery, Energy
Error, exclamation, wrong
flask, warning, wrong
Jar, exclamation, warning
Hourglass, exclamation, wrong
Mixed
Smooth
Application, warning
Shopping & e-commerce
Pretty Office part 3
warning, globe
256x256
Business & finance
warning, Blue