In the Qt version of Meow, on Linux and Windows, it's possible to change all the icons.

The icons go into ~/.config/ on Linux and c:\users\<username>\\ on Windows.

Icon Name Purpose
meow.png Application icon
list-add.png Add a file
list-media-playback-pause.png Paws
list-media-playback-start.png Play
media-skip-backward.png Previous
media-skip-forward.png Next
player-volume.png Volume

Default icons are from Oxygen.