Membership site for vintage graphics - would it work?

I have a large collection of public domain images that I will soon publish on my site (made in wordpress) - I'm torn between starting a membership site or selling each set individually. Has anyone tried something similar?

1. Do you think people would pay to get access to brushes/vectors like these?

http://www.flickr.com/photos/thevintagecollective/sets/

2. What membership plugin would you recommend for wordpress? It would be great if the number of downloads/month could be limited in some way to get subscribers to stay longer.

Well, you won't make any money by having them posted on flickr

I could argue this both ways...

paid:

free: (usually also offering other design elements)

Obviously both can be done, and both can be well monetized... I would think that given that the images are public domain and could probably be gotten for free elsewhere, selling them is going to be a little harder, but someone will probably buy it... Maybe if you sell it as a download + CD...

Or - the third route - free download for registered members (this way you make a list and then upsell them other things) + start adding as much other stuff to download as possible.

Personally, I think this may be a difficult sell given the large number of free vectors available, but flavaFX does pretty well, sooo??????