You've got quite a challenge, wanting to mix 60s retro and antique! I would advise choosing one to focus on
A good place to start would be deciding what color scheme and patterns you want to base your designs around. Nice retro colors are brown with some mixture of a less natural tone, like orange and red perhaps. As for shapes, it can be as simple as something like squares with rounded corners, or circles/ovals.
Remember that the 60's were psychedelic times, so trippy type stuff is what you might be looking for.
Here's a thread with an idea for a design:http://www.craftster.org/forum/index.php?topic=49986.0
And here's a website for a little more inspiration:http://www.classic-modern.co.uk/index.htm
Keep us posted if you come up with any ideas