I am trying to create a directory website that would be for tattoo artists in a particular niche of tattoo design. I want to initially list different artists for free to gain momentum and maybe eventually charge artists to place ads on the site. So my question is this: in initially listing different artists for free, what is appropriate and what is not in terms of showcasing their content? For example can I take pictures from their website since I am actually advertising their website in order to direct people to it?
If you link to their website and use images located on their site there should be no issue. By "images on their site" I mean don't upload them to your server, hotlink to their images, assuming they aren't blocking hotlinks.
But why don't you contact them and explain what you are doing and ask for permission. It is pretty unusual for a business to say no to someone wanting to promote their services.