location of small user account logo pictures

Hi all,

in mountain lion every user or user account has such a small logo image you can choose. I would like to change this to a custom logo and there for would like to know where these image files are located because I am not able to find them on my new imac.

Also need to know what the optimal image size for such a logo is but I guess I will find that out one I found them.

Thanks in advance for your help.

Regards,
tom

Just drag in any picture you like into picture area in the Users and groups preferences and it will become the piccy for that user account

thanks a lot louishen..... cannot believe it is so simple, obviously I´m still used to complicated windows stuff.

Thanks and regards,
Tom