I painted these glass pieces with the help of frogtape.  I like the look of glass and plants and they naturally go together very well.  Plants add life to a room and the glass adds shine and airiness...(< yes that's a strange word) ;)  Anyways, I've decided pretty much anything can be painted.  Of course this finish won't be as durable as a fired glaze and don't count on being able to use Windex on these pieces or even water but I've had these done for three years now and they still look good.  I brushed on the fishbowl paint with acrylic and the silver bowl was spray painted. Recently, I painted a mirror with Martha Stewart craft paint and it seems to hold up well too.  Here's another example of a painted glass/mirror.