Let’s find the best photo taken by your followers recently and repost it to your own channel. Do ask for permission if you can. Doing this last-minute? Then make the shout-out (giving credits) extra clear. If someone’s profile is set to public, they often won’t mind the repost anyway. I’ve never had trouble with this (ever!).
Do make sure to give those credits though, either in the picture and in the caption, or one of the two.
Also, add some words of gratitude, and tell people what the reposts mean to you. This will help in building a relationship and stimulating engagement.