This may not be an effective tactic at all, but it amuses me so I'm going to keep on doing it anyway whether it works or not.
I like playing around with found images, making them into art and memes, as well as editing my own photos and art. So I end up with hundreds of images that mostly end up sitting unseen in folders on my computer.
If I sign them with a whopping great "www.sift.co.nz" URL they become digital billboards for my blog. It's likely very few people will notice them, let alone go to the trouble of typing out the address and actually visiting the blog, but too bad, I think blog posts look better with more images.
They are fairly varied images, but to keep a consistent style I'm doing them all in a 1x1 ratio which I just like the look of.
