Your postcard can be pretty much anything, just as long as it looks antiqued - often, simple sepia or b/w treatment works for this.
Yes, you can do nudes (tasteful please), people, beach and other scenes, anything that would make a great postcard.
If you\'ve seen old erotica or old postcards then you\'ll know what i mean, but as long as whatever you post looks older - treated or otherwise - you need not be a great artist to post! -- then your work is welcome.
Porn and other images like will be deleted. Sorry, but there are plenty of groups for this on Flickr and we want art nudes if we have them.
Invite your friends, join, post, have fun, and get creative... Who knows, you might discover you could start a postcard company for a living...