PNG MORE
Mixed
Pixel
IconSweets 2
Alert, Information, Biu
Black
40x40
Alert, Information
Alert, warning, paper
Alert, warning
PNG ICO ICNS MORE
Signs & symbols
Kiwi
Alert
32x32
Arrows
Sanscons
64x64
UI
Gnome icons
severe, Alert, weather
Desktop apps
Splashyfish
notice, Alert, triangle
16x16
DRF
Attention, Alert, exclamation