Can I use any PNG image as an icon?

[Old_Professor]

I want to change the icon for an app on my home screen. I found Icon Changer Free, which seems to do what I want. I want to use a picture for the icon. On Windows I have to change the picture format to ICO. I found one mention that Android icons are just PNG files. Is that correct? Can I use any PNG as an icon?

 

[Indoler]

I'm sure the proof of the pudding is in the eating, professor.