There seems to be no golden bullet to prevent imgur's policy change from wiping out a lot of the existing content on a subreddit. The best that we can do is download content that we want to preserve onto our computers or to a different hosting site. I'll be using imgchest.com, since it is functionally very similar to imgur, but still permits hidden NSFW posts. But you can use whatever tools you want, there are a few suggested on r/ImgurAlternatives.

This will be mostly user-driven; I can't do it all myself. So if there is some content that you really want to preserve, you should make sure that you download it. If everyone just picks a few of their favorites, the best and most relevant content on the sub will still be available even after the purge.

Once stuff starts disappearing, I will put out a call for everyone to repost any favorites that have been wiped out. Again, please don't start spamming until I give the go-ahead. During the reposting period, all the posting rules will still apply, and I will be moderating new posts as they come in. Make sure your content complies with the rules in the sidebar and on the posting page.

Since we're a relatively small sub, we can come out of this without too much lost content, as long as everyone pitches in a little!