You can make your popup menu have a submenu of preview and show...
menu nicklist {
Color nick red
.Preview:echo -a 04 $+ $1
.Show:msg $active 04 $+ $1
Color nick green
.Preview:echo -a 09 $+ $1
.Show:msg $active 09 $+ $1
}
And so on. That's an easy way to get a preview. You could also use $tip to get a popup in the lower right...
For the preview parts of the menu-
.Preview:noop $tip(Preview,Preview,09 $+ $1),$null,$readini($mircini,files,trayicon),1,$null,$null)
Just change the 09 $+ $1 part. Of course, you can adjust the rest as well if you want to. /help $tip
If you want a tooltip on the menu itself, you'd need a DLL. I'm not sure if there are any that do that already or if you'd have to make one.