Assuming you're talking about photos that you have posted in threads - you can't. They are a permanent part of the thread and removing them would disrupt the continuity of the information posted there.
You can remove them from your photo album, but that is not likely what you are talking about.
I'm in the same situation.
Your other alternative is to upgrade your account which gives you more photo space.
Dave
Hi Dave,
I tried to post an image today and was notified I had used my quota. You got to the bottom of my problem right away, upgrade or stop posting images.
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