Here’s a few things that come to mind…
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If you’re going to use somebody else’s photos, you should ask them for permission to do it.
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I think there are photos on Wikipedia that have a form of licencing which lets you use them without asking.
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If you have your own domain and server space, you should copy the picture files there so you can make sure they’ll still be available in a few years.
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If you don’t have your own server space, then you should upload them to Imgur and then grab the URL that ends in .jpg or .gif etc (by right-clicking the uploaded photo on Imgur).
I use an account on Imgur (free) and that lets me get back to my collection of uploads any time. There must be other sites that work like Imgur as well.