There are skin options, by going to the Messenger Plus! Live button on the contact list, the Messenger Skin and then Skin Options.
From there a window will open, you will be looking for the option for contact list display picture size. It will be a drop down list (if I know Willz
) and you can select the size from there.
Once you exit the options window by clicking OK, Messenger will need to restart to apply the new changes