So this is how you make money with tumblr?

I'm not really into the whole tumblr thing as a blogger but I must admit I do visit a fair number of tumblr sites to check out the pics of hot guys (hey, I'm human!).

I've recently been thinking about how gay webmasters make any money from these sites since outright advertising or affiliate links are not allowed.

So correct me if I'm wrong, but if you want to monetize your tumblr site is the proper technique to post a ton of pics from other tumblr sites but every now and then insert a pic that links back to one of your blogs that has sponsor ads on it? If your tumblr site gets a lot of traffic a surfer might click on that "magic pic" that links back to your blog where they will see your sponsor banners and hopefully you'll make some money.

Or is there some other trick I'm missing?