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Forum Moderators: not2easy
Ask for permission, and if you don't get it, look for other images until you get a permission in writing.
I suggest to not go and just take images as you see fit. You might find yourself in copyright infringement trouble and DMCA complaints rather quickly.
This doesn't always work but does some of the time. YOu might even build a good relationship with the owner of a related site.
If they say no forget it.
The mention of DMCA above was brief. But what it means is that if I find someone who has stolen my content, I can have their site shut down by the end of the day, and have it removed from the search engine listings in a few days. Bear that in mind if you're considering taking risks with copyright. One little stolen picture, video, music file, or article can put you out of business.