PNG ICO ICNS MORE
Computer & hardware
3D
Human o2
Dialog, warning
Black
128x128
UI
Pixel
Fugue Icons
compile, warning
16x16
Desktop apps
Splashyfish
notice, Alert, triangle
Tango
warning, Dialog
32x32
Family & home
Cartoon
Kids
Critical, Attention, Error
Smooth
Crystal Project
messagebox, warning
256x256
Futurosoft
Adept, warning, notifier
Glaze
warning, messagebox, Alert
64x64
KDE Crystal Diamond
22x22
Nuvola
warning, important, Attention
Crystal Clear
Info, warning