There’s a somewhat unintuitive way you could do this, but I’m not sure if it’s what you’re looking for:
You could basically use the photo description or caption to choose a featured image. For example, in your gallery, you could edit one photo that you “tag” by entering a key word in the description field… maybe “featured”.
Then in your code, you could loop through the gallery images and when you find the image with the description “featured” you could display that and skip over all the others.
I could supply a code snippet, but I wasn’t sure if this would be a good enough solution. I don’t know of any other way to tack on an extra checkbox on the edit window.
