PNG ICO ICNS MORE
UI
Pixel
Fugue Icons
tick, shield, ok
Green
16x16
ok, Check, tick
Check, Mix, ui
Gray
ui, Box, Check
Smooth
Elegant Blue Web
Check, 34
SteelBlue
64x64
Ultimate Gnome
ok, yes, Check
Black
256x256
Check
Firebrick
mark, mail, Check
WhiteSmoke
PNG MORE
BWPX
Check, bullet
Silver
18x18
success, ok, yes
Gnome icons
Check, macro, Brackets
24x24
Check, filled
tick, frame, Check
DarkSlateGray
ok, shield, Check
Accept, Circle, tick
Check, ok, tick
tick, Check
3D
Glaze
Blue, Apply, Check
CornflowerBlue
green, ok, Check
YellowGreen
Check, correct, yes
ForestGreen
48x48
Function icons
Error, warning, Info
DarkRed
Nuvola
yes, Check, good
Crystal Clear
on, select, correct
128x128
ok, good, yes