PNG ICO ICNS MORE
UI
Glyph
Round UI Buttons
ok, tick, yes
OliveDrab
512x512
tick, yes, Go
DeepSkyBlue
PNG ICO ICNS SVG MORE
Outline
Linecon
tick, success, yes
Black
iOS Tab Bar
complete, done, Circle
ok, Circle, done
Google Material Design icons
done, Cloud
done
All, done
ikooni outline: Free Basic
checkmark, Check, complete
Very Basic. Android L (Lollipop)
done, check mark, good
Free basic
Accept, checkmark, Check
DarkSeaGreen
Pixel
Boolean
square, done
16x16
Gnome icons
followup, for, flag
48x48
Fugue Icons
Accept, Circle, tick
Green