Most icons are from the Tango icon set. The other ones come from:

OpenClipArt license: https://openclipart.org/share


DOS icon
https://commons.wikimedia.org/wiki/File:Contrived_MS-DOS_logo.svg

Umbrella, based on
https://openclipart.org/detail/226065/open-umbrella

Cube icon, based on
https://openclipart.org/detail/168258/3d-cube-icon

Beach ball, based on
https://openclipart.org/detail/172888/simple-beach-ball

Column
https://openclipart.org/detail/25388/architetto-capitello-modanatura

Crayon-drawed icon, combined from the icons
https://upload.wikimedia.org/wikipedia/commons/thumb/b/b5/Format-justify-fill.svg/48px-Format-justify-fill.svg.png
https://openclipart.org/detail/85387/crayon
https://openclipart.org/detail/161623/crayon-star

Domino
https://openclipart.org/detail/3525/domino-set-15

Soccer ball
https://openclipart.org/detail/21992/soccer-ball

Race flag
https://openclipart.org/detail/62779/wavy-checkered-flag

Semaphore, based on
https://openclipart.org/detail/66427/traffic-semaphore-red-light
https://openclipart.org/detail/66433/traffic-semaphore-yellow-light
https://openclipart.org/detail/66421/traffic-semaphore-green-light

Crossed swords
https://openclipart.org/detail/3058/crossed-swords

Shield and sword, based on
Tango shield icon, and
https://openclipart.org/detail/22432/toy-sword